Microorganisms

Open AccessArticle

UranyLess Low Voltage Transmission Electron Microscopy: A Powerful Tool for Ultrastructural Studying of Cyanobacterial Cells

by

,

,

,

,

,

and

Microorganisms 2023, 11(4), 888; https://doi.org/10.3390/microorganisms11040888 (registering DOI) - 29 Mar 2023

Abstract

Sample preparation protocols for conventional high voltage transmission electron microscopy (TEM) heavily rely on the usage of staining agents containing various heavy metals, most commonly uranyl acetate and lead citrate. However high toxicity, rising legal regulations, and problematic waste disposal of uranyl acetate [...] Read more.

Sample preparation protocols for conventional high voltage transmission electron microscopy (TEM) heavily rely on the usage of staining agents containing various heavy metals, most commonly uranyl acetate and lead citrate. However high toxicity, rising legal regulations, and problematic waste disposal of uranyl acetate have increased calls for the reduction or even complete replacement of this staining agent. One of the strategies for uranyless imaging is the employment of low-voltage transmission electron microscopy. To investigate the influence of different imaging and staining strategies on the final image of cyanobacterial cells, samples stained by uranyl acetate with lead citrate, as well as unstained samples, were observed using TEM and accelerating voltages of 200 kV or 25 kV. Moreover, to examine the possibilities of reducing chromatic aberration, which often causes issues when imaging using electrons of lower energies, samples were also imaged using a scanning transmission electron microscopy at 15 kV accelerating voltages. The results of this study demonstrate that low-voltage electron microscopy offers great potential for uranyless electron microscopy. Full article

(This article belongs to the Special Issue New Methods in Microbial Research 3.0)

Open AccessArticle

Helicobacter pylori and Human Immunodeficiency Virus Co-Infection: Potential Implications for Future Gastric Cancer Risk

by

,

,

,

and

Microorganisms 2023, 11(4), 887; https://doi.org/10.3390/microorganisms11040887 (registering DOI) - 29 Mar 2023

Abstract

Objective: Helicobacter pylori and human immunodeficiency virus (HIV) are both pandemic infections with variable geographic prevalence rates. H. pylori–HIV co-infection at the regional and sub-regional levels with a perspective on gastric cancer incidence is discussed. Design: Based on PRISMA guidelines, national data [...] Read more.

Objective: Helicobacter pylori and human immunodeficiency virus (HIV) are both pandemic infections with variable geographic prevalence rates. H. pylori–HIV co-infection at the regional and sub-regional levels with a perspective on gastric cancer incidence is discussed. Design: Based on PRISMA guidelines, national data for H. pylori, HIV, and H. pylori–HIV co-infection were collected for the general population through December 2019. Joint temporal and geographical data for H. pylori and HIV infections in 48 countries were available and used to generate H. pylori–HIV co-infection estimates by cross-sectional analysis. These data were compared with gastric carcinoma statistics for the same countries. Results: The estimated global prevalence rate of H. pylori–HIV co-infection was 1.7 per 1000 people, representing 12.6 million people. Prevalence according to region was, in decreasing order, sub-Saharan Africa 21.9‰, Eastern Europe/Central Asia 4.3‰, Latin America/Caribbean 2.0 ‰, North America/Western/Southern/Northern Europe 1.1‰, Asia/Pacific 0.8‰, and North Africa/Middle East 0.1 ‰. The incidence and mortality rates for gastric carcinoma were higher in East/Pacific Asia, Southern/Andean Latin America, and Eastern Europe regions, and the incidence appeared to be 1.8-fold greater in H. pylori–HIV-infected people in East Asia. Conclusions: The population at risk of H. pylori–HIV co-infection is estimated to be 12.6 million people (2015 reference year). The heterogeneity of H. pylori–HIV co-infection across regions and sub-regions does not show a clear association with gastric carcinoma. Other methodological approaches with analytical studies (cohort, case–control) are required to measure the potential effect of H. pylori infection and its treatment on the incidence of gastric carcinoma in the large HIV–H. pylori-positive cohort. Full article

(This article belongs to the Special Issue Advances in the Diagnosis and Treatment of Helicobacter pylori)

► Show Figures

Figure 1

Open AccessArticle

Green Synthesized Silver Nanoparticles: A Novel Approach for the Enhanced Growth and Yield of Tomato against Early Blight Disease

by

,

,

,

,

,

Muhammad Tajammal Khan

,

Inzamam Ul Haq

and

Qamar uz Zaman

Microorganisms 2023, 11(4), 886; https://doi.org/10.3390/microorganisms11040886 (registering DOI) - 29 Mar 2023

Abstract

Tomato plants are among the most widely cultivated and economically important crops worldwide. Farmers’ major challenge when growing tomatoes is early blight disease caused by Alternaria solani, which results in significant yield losses. Silver nanoparticles (AgNPs) have gained popularity recently due to [...] Read more.

Tomato plants are among the most widely cultivated and economically important crops worldwide. Farmers’ major challenge when growing tomatoes is early blight disease caused by Alternaria solani, which results in significant yield losses. Silver nanoparticles (AgNPs) have gained popularity recently due to their potential antifungal activity. The present study investigated the potential of green synthesized silver nanoparticles (AgNPs) for enhancing the growth and yield of tomato plants and their resistance against early blight disease. AgNPs were synthesized using leaf extract of the neem tree. Tomato plants treated with AgNPs showed a significant increase in plant height (30%), number of leaves, fresh weight (45%), and dry weight (40%) compared to the control plants. Moreover, the AgNP–treated plants exhibited a significant reduction in disease severity index (DSI) (73%) and disease incidence (DI) (69%) compared to the control plants. Tomato plants treated with 5 and 10 ppm AgNPs reached their maximum levels of photosynthetic pigments and increased the accumulation of certain secondary metabolites compared to the control group. AgNP treatment improved stress tolerance in tomato plants as indicated by higher activities of antioxidant enzymes such as PO (60%), PPO (65%), PAL (65.5%), SOD (65.3%), CAT (53.8%), and APX (73%). These results suggest that using green synthesized AgNPs is a promising approach for enhancing the growth and yield of tomato plants and protecting them against early blight disease. Overall, the findings demonstrate the potential of nanotechnology-based solutions for sustainable agriculture and food security. Full article

(This article belongs to the Special Issue Nanoparticles and Their Biological Applications: Recent Advances in 2022–2023)

► Show Figures

Figure 1

Open AccessArticle

Diverse Repertoire and Relationship of Exopolysaccharide Genes in Cold-Adapted Acinetobacter sp. CUI-P1 Revealed by Comparative Genome Analysis

by

,

,

,

,

,

and

Microorganisms 2023, 11(4), 885; https://doi.org/10.3390/microorganisms11040885 (registering DOI) - 29 Mar 2023

Abstract

This study focused on the exploration of microbial communities inhabiting extreme cold environments, such as the Passu and Pisan glaciers of Pakistan, and their potential utilization in industrial applications. Among the 25 initially screened strains, five were found to be suitable candidates for [...] Read more.

This study focused on the exploration of microbial communities inhabiting extreme cold environments, such as the Passu and Pisan glaciers of Pakistan, and their potential utilization in industrial applications. Among the 25 initially screened strains, five were found to be suitable candidates for exopolysaccharide (EPS) production, with strain CUI-P1 displaying the highest yield of 7230.5 mg/L compared to the other four strains. The purified EPS from CUI-P1 was tested for its ability to protect probiotic bacteria and E. coli expressing green fluorescence protein (HriGFP) against extreme cold temperatures, and it exhibited excellent cryoprotectant and emulsification activity, highlighting its potential use in the biotechnological industry. Furthermore, the genome of Acinetobacter sp., CUI-P1 comprised 199 contigs, with a genome size of 10,493,143bp and a G + C content of 42%, and showed 98.197% nucleotide identity to the type genome of Acinetobacter baumannii ATCC 17978. These findings offer promising avenues for the application of EPS as a cryoprotectant, an essential tool in modern biotechnology. Full article

(This article belongs to the Section Microbial Biotechnology)

► Show Figures

Figure 1

Open AccessArticle

Viral Identification Using Multiplex Polymerase Chain Reaction Testing Does Not Reduce Antibiotic Prescribing in Paediatric Intensive Care Units

by

Aurélie Hayotte

,

Patricia Mariani-Kurkdjian

,

,

,

,

,

and

Microorganisms 2023, 11(4), 884; https://doi.org/10.3390/microorganisms11040884 (registering DOI) - 29 Mar 2023

Abstract

PCR tests for viral identification, performed on nasopharyngeal secretions, have experienced a major boom in the last few years. Their use is very frequent, but their indications are still not well defined, especially in Paediatric Intensive Care Units (PICU). These tests are used [...] Read more.

PCR tests for viral identification, performed on nasopharyngeal secretions, have experienced a major boom in the last few years. Their use is very frequent, but their indications are still not well defined, especially in Paediatric Intensive Care Units (PICU). These tests are used for the microbiological diagnosis of lower respiratory infections but can be used in other situations. The aim of the study was to investigate the effect of viral identification on antibiotic therapy management. We conducted a single-centre retrospective study from 1 October 2017 to 31 December 2019. This study included all consecutive FilmArray^® Respiratory Panel tests performed in patients hospitalised in a PICU. Patients were identified using the microbiology laboratory prospective database and data were extracted from the medical record. 544 tests corresponding to 408 patients were included. The main reasons for testing were pneumonia (34%) and bronchiolitis (24%). In 70% of cases, at least one virus was identified, with Human Rhinovirus (56%) and Respiratory Syncytial Virus (28%) being the two predominant. Bacterial co-infection was present in 25% of cases. Viral identification was not associated with reduced antibiotic therapy. On multivariate analysis, antibiotic management was significantly associated with clinical gravity, CRP value or radiology findings regardless of virus identification. Viral identification has an epidemiological value, but antibiotic prescription relies on other factors. Full article

(This article belongs to the Special Issue Infectious Diseases: Clinical Diagnosis and Molecular Epidemiology 2.0)

► Show Figures

Figure 1

Open AccessArticle

Bioaccessibility of Maillard Reaction Products from Biscuits Formulated from Buckwheat Flours Fermented by Selected Lactic Acid Bacteria

by

Małgorzata Wronkowska

,

Dorota Szawara-Nowak

,

Mariusz Konrad Piskuła

and

Henryk Zieliński

Microorganisms 2023, 11(4), 883; https://doi.org/10.3390/microorganisms11040883 (registering DOI) - 29 Mar 2023

Abstract

The in vitro bioaccessibility of the soluble protein and Maillard reaction products (MRPs) such as furosine (an early indicator of the MR), free FIC (fluorescent intermediate compounds), and FAST index (fluorescence of advanced MRPs and tryptophan), and the level of melanoidins defined by [...] Read more.

The in vitro bioaccessibility of the soluble protein and Maillard reaction products (MRPs) such as furosine (an early indicator of the MR), free FIC (fluorescent intermediate compounds), and FAST index (fluorescence of advanced MRPs and tryptophan), and the level of melanoidins defined by the browning index were analyzed in biscuits formulated from raw and roasted common buckwheat flours fermented by select lactic acid bacteria (LAB). The content of soluble proteins in fermented buckwheat flour and biscuits before and after digestion in vitro was significantly dependent on the LAB applied and the type of flour used and was the highest in the digested biscuits, indicating increased bioaccessibility. Generally, in all analyzed biscuits a lower furosine content was observed as compared to control samples, and its high bioaccessibility was noted after digestion. The free FIC in biscuits was strain-dependent, resulting in low bioaccessibility with the exception of biscuits obtained from both types of flours fermented by Streptococcus thermophilus MK-10. Compared to control biscuits obtained from raw buckwheat flour, the almost twice-increased FAST index was found for samples fermented by L. plantarum IB or Streptococcus thermophilus MK-10. After digestion, at least a fivefold higher value of the browning index was noted in control and tested biscuits, indicating the high bioaccessibility of melanoidins. This study indicates that fermentation of buckwheat flours by selected lactic acid bacteria seems to be a good way to obtain a product with high bioaccessibility of MRPs. However, further research on their functional properties is needed. Full article

(This article belongs to the Special Issue Microorganisms and Fermented Foods 2.0)

► Show Figures

Figure 1

Open AccessArticle

Effects of Dispersant on the Petroleum Hydrocarbon Biodegradation and Microbial Communities in Seawater from the Baltic Sea and Norwegian Sea

by

,

,

,

,

,

and

Microorganisms 2023, 11(4), 882; https://doi.org/10.3390/microorganisms11040882 (registering DOI) - 29 Mar 2023

Abstract

Dispersants have been used in several oil spill accidents, but little information is available on their effectiveness in Baltic Sea conditions with low salinity and cold seawater. This study investigated the effects of dispersant use on petroleum hydrocarbon biodegradation rates and bacterial community [...] Read more.

Dispersants have been used in several oil spill accidents, but little information is available on their effectiveness in Baltic Sea conditions with low salinity and cold seawater. This study investigated the effects of dispersant use on petroleum hydrocarbon biodegradation rates and bacterial community structures. Microcosm experiments were conducted at 5 °C for 12 days with North Sea crude oil and dispersant Finasol 51 with open sea Gulf of Bothnia and coastal Gulf of Finland and Norwegian Sea seawater. Petroleum hydrocarbon concentrations were analysed with GC-FID. Bacterial community structures were studied using 16S rDNA gene amplicon sequencing, and the abundance of genes involved in hydrocarbon degradation with quantitative PCR. The highest oil degradation gene abundances and oil removal were observed in microcosms with coastal seawater from the Gulf of Bothnia and Gulf of Finland, respectively, and the lowest in the seawater from the Norwegian Sea. Dispersant usage caused apparent effects on bacterial communities in all treatments; however, the dispersant’s effect on the biodegradation rate was unclear due to uncertainties with chemical analysis and variation in oil concentrations used in the experiments. Full article

(This article belongs to the Special Issue Oil Biodegradation and Bioremediation in Cold Marine Environment 2.0)

► Show Figures

Figure 1

Open AccessArticle

Features of Engorgement of Ixodes ricinus Ticks Infesting the Northern White-Breasted Hedgehog in an Urban Park

by

László Egyed

,

Dávidné Nagy

and

Zsolt Lang

Microorganisms 2023, 11(4), 881; https://doi.org/10.3390/microorganisms11040881 (registering DOI) - 29 Mar 2023

Abstract

In this work we exploited the parallel dense tick and hedgehog populations of an urban park in Budapest, Hungary as a good host–parasite model to obtain detailed data about this physiological relationship. Over a 27-week period from April to October, 57 hedgehogs were [...] Read more.

In this work we exploited the parallel dense tick and hedgehog populations of an urban park in Budapest, Hungary as a good host–parasite model to obtain detailed data about this physiological relationship. Over a 27-week period from April to October, 57 hedgehogs were captured in an urban park and kept for 10–14 days in animal house. All dropped off ticks were sampled, which allowed us to draw more a detailed picture of Ixodes ricinus–hedgehog relationships. The results indicated that the hedgehog is an effective host for ticks (prevalence: 100%) and the mean intensity of infestation was 83.25. Of the male ticks, 68.42% dropped off dead; 1.56% of the dropped off nymphs and 11.4% of the larvae finished their bloodmeal with red cuticles, while 5.79% of the females could not finish their blood meal, and dropped off dried, dead, or shrunken. We applied novel statistical methods of survival analysis of prevalent cohorts to estimate the whole attachment times of ticks from the observed attachment times, having no information about when the ticks attached to their hosts. Mean attachment times were 4 days for larvae, 5 days for nymphs, 10 days for females, and 8 days for males. On the first day after capture of the hosts, fewer females, nymphs, and larvae detached engorged than had been predicted, but this was not true for males. Mean intensity of infestation per host was 1.4 for males, 6.7 for females, 45.0 for nymphs, and 29.3 for larvae. As regards seasonality, the activity of all stages of ticks consisted of several smaller peaks and considerably differed by season. Studies of the dense tick–host populations of this natural habitat could provide further valuable data about tick–host relations, the data of which cannot be drawn from most other hedgehog habitats. Full article

(This article belongs to the Special Issue Ticks and Tick-Borne Diseases in Animals)

► Show Figures

Figure 1

Open AccessArticle

Gut Dysbiosis: A Target for Protective Interventions against Parkinson’s Disease

by

,

,

,

,

,

and

Microorganisms 2023, 11(4), 880; https://doi.org/10.3390/microorganisms11040880 - 29 Mar 2023

Abstract

Sub-chronic inflammation, caused by age-related dysbiosis, primes the brain to neuroinflammation and neurodegenerative diseases. Evidence revealed that Parkinson’s disease (PD) might originate in the gut, demonstrating gastro-intestinal disturbances, as reported by PD patients long before developing motor symptoms. In this study, we conducted [...] Read more.

Sub-chronic inflammation, caused by age-related dysbiosis, primes the brain to neuroinflammation and neurodegenerative diseases. Evidence revealed that Parkinson’s disease (PD) might originate in the gut, demonstrating gastro-intestinal disturbances, as reported by PD patients long before developing motor symptoms. In this study, we conducted comparative analyses in relatively young and old mice maintained in conventional or gnotobiotic conditions. We aimed to confirm that the effects induced by age-related dysbiosis, rather than aging itself, sensitize to PD onset. This hypothesis was confirmed in germ-free (GF) mice, which proved resistant to the pharmacological induction of PD, regardless of their age. Contrary to conventional animals, old GF mice did not develop an inflammatory phenotype or an accumulation of iron in the brain, two catalysts sensitizing to disease onset. The resistance of GF mice to PD is reverted when colonized with stool collected from conventional old animals, but not if receiving bacterial content from young mice. Hence, changes in gut microbiota composition are a risk factor for PD development and can be targeted preventively by iron chelators, shown to protect the brain from pro-inflammatory intestinal priming that sensitizes to neuroinflammation and the development of severe PD. Full article

(This article belongs to the Special Issue Lifestyle, Gut Microbiota and Health 2.0)

► Show Figures

Figure 1

Open AccessArticle

Effects of Inbreeding on Microbial Community Diversity of Zea mays

by

Corey R. Schultz

,

Matthew Johnson

and

Jason G. Wallace

Microorganisms 2023, 11(4), 879; https://doi.org/10.3390/microorganisms11040879 - 29 Mar 2023

Abstract

Heterosis, also known as hybrid vigor, is the basis of modern maize production. The effect of heterosis on maize phenotypes has been studied for decades, but its effect on the maize-associated microbiome is much less characterized. To determine the effect of heterosis on [...] Read more.

Heterosis, also known as hybrid vigor, is the basis of modern maize production. The effect of heterosis on maize phenotypes has been studied for decades, but its effect on the maize-associated microbiome is much less characterized. To determine the effect of heterosis on the maize microbiome, we sequenced and compared the bacterial communities of inbred, open pollinated, and hybrid maize. Samples covered three tissue types (stalk, root, and rhizosphere) in two field experiments and one greenhouse experiment. Bacterial diversity was more affected by location and tissue type than genetic background for both within-sample (alpha) and between-sample (beta) diversity. PERMANOVA analysis similarly showed that tissue type and location had significant effects on the overall community structure, whereas the intraspecies genetic background and individual plant genotypes did not. Differential abundance analysis identified only 25 bacterial ASVs that significantly differed between inbred and hybrid maize. Predicted metagenome content was inferred with Picrust2, and it also showed a significantly larger effect of tissue and location than genetic background. Overall, these results indicate that the bacterial communities of inbred and hybrid maize are often more similar than they are different and that non-genetic effects are generally the largest influences on the maize microbiome. Full article

(This article belongs to the Special Issue Advances in Plant-Microbe Interactions)

► Show Figures

Figure 1

Open AccessArticle

A Streamlined Approach for Fluorescence Labelling of Low-Copy-Number Plasmids for Determination of Conjugation Frequency by Flow Cytometry

by

Qin Qi

,

Muhammad Kamruzzaman

and

Jonathan R. Iredell

Microorganisms 2023, 11(4), 878; https://doi.org/10.3390/microorganisms11040878 - 29 Mar 2023

Abstract

Bacterial conjugation plays a major role in the dissemination of antibiotic resistance and virulence traits through horizontal transfer of plasmids. Robust measurement of conjugation frequency of plasmids between bacterial strains and species is therefore important for understanding the transfer dynamics and epidemiology of [...] Read more.

Bacterial conjugation plays a major role in the dissemination of antibiotic resistance and virulence traits through horizontal transfer of plasmids. Robust measurement of conjugation frequency of plasmids between bacterial strains and species is therefore important for understanding the transfer dynamics and epidemiology of conjugative plasmids. In this study, we present a streamlined experimental approach for fluorescence labelling of low-copy-number conjugative plasmids that allows plasmid transfer frequency during filter mating to be measured by flow cytometry. A blue fluorescent protein gene is inserted into a conjugative plasmid of interest using a simple homologous recombineering procedure. A small non-conjugative plasmid, which carries a red fluorescent protein gene with a toxin–antitoxin system that functions as a plasmid stability module, is used to label the recipient bacterial strain. This offers the dual advantage of circumventing chromosomal modifications of recipient strains and ensuring that the red fluorescent protein gene-bearing plasmid can be stably maintained in recipient cells in an antibiotic-free environment during conjugation. A strong constitutive promoter allows the two fluorescent protein genes to be strongly and constitutively expressed from the plasmids, thus allowing flow cytometers to clearly distinguish between donor, recipient, and transconjugant populations in a conjugation mix for monitoring conjugation frequencies more precisely over time. Full article

(This article belongs to the Section Antimicrobial Agents and Resistance)

► Show Figures

Figure 1

Open AccessArticle

Effect of Methionine on Gene Expression in Komagataella phaffii Cells

by

,

,

,

,

,

,

,

and

Microorganisms 2023, 11(4), 877; https://doi.org/10.3390/microorganisms11040877 (registering DOI) - 29 Mar 2023

Abstract

Komagataella phaffii yeast plays a prominent role in modern biotechnology as a recombinant protein producer. For efficient use of this yeast, it is essential to study the effects of different media components on its growth and gene expression. We investigated the effect of [...] Read more.

Komagataella phaffii yeast plays a prominent role in modern biotechnology as a recombinant protein producer. For efficient use of this yeast, it is essential to study the effects of different media components on its growth and gene expression. We investigated the effect of methionine on gene expression in K. phaffii cells using RNA-seq analysis. Several gene groups exhibited altered expression when K. phaffii cells were cultured in a medium with methanol and methionine, compared to a medium without this amino acid. Methionine primarily affects the expression of genes involved in its biosynthesis, fatty acid metabolism, and methanol utilization. The AOX1 gene promoter, which is widely used for heterologous expression in K. phaffii, is downregulated in methionine-containing media. Despite great progress in the development of K. phaffii strain engineering techniques, a sensitive adjustment of cultivation conditions is required to achieve a high yield of the target product. The revealed effect of methionine on K. phaffii gene expression is important for optimizing media recipes and cultivation strategies aimed at maximizing the efficiency of recombinant product synthesis. Full article

(This article belongs to the Special Issue Yeasts Biochemistry and Biotechnology)

► Show Figures

Figure 1

Open AccessArticle

The Gut Microbiota of Broilers Reared with and without Antibiotic Treatment

by

,

,

,

and

Microorganisms 2023, 11(4), 876; https://doi.org/10.3390/microorganisms11040876 - 29 Mar 2023

Abstract

The aim of this study was to examine the microbiota in broilers reared with and without antibiotics and to investigate differences between the upper, middle and lower sections of the gastrointestinal tract (GIT). One of two commercial flocks was treated with an antibiotic [...] Read more.

The aim of this study was to examine the microbiota in broilers reared with and without antibiotics and to investigate differences between the upper, middle and lower sections of the gastrointestinal tract (GIT). One of two commercial flocks was treated with an antibiotic (T) (20 mg trimethoprim and 100 mg sulfamethoxazole per ml in the drinking water for 3 days) and the other was left untreated (UT). The GIT contents of 51 treated and untreated birds were aseptically removed from the upper (U), middle (M) and lower (L) sections. These were pooled in triplicate (n = 17 per section per flock), the DNA extracted and purified, 16S amplicon metagenomic sequencing performed and the resultant data analysed using a range of bioinformatics software. There were significant differences in the microbiota of the upper, middle and lower GIT, and treatment with the antibiotic significantly affected the microbiota in each of these sections. This study provides new data on broiler GIT microbiota and suggests that GIT location is a more important determinant of the constituent bacterial flora rather than the use or otherwise of antimicrobial treatments, at least when applied early in the production cycle. Full article

(This article belongs to the Special Issue Gut Microbiome of Farm Animals in Health and Disease 2.0)

► Show Figures

Figure 1

Open AccessArticle

Phenotypic and Molecular Characteristics of Carbapenem-Resistant Acinetobacter baumannii Isolates from Bulgarian Intensive Care Unit Patients

by

,

,

,

and

Microorganisms 2023, 11(4), 875; https://doi.org/10.3390/microorganisms11040875 - 29 Mar 2023

Abstract

Carbapenem-resistant Acinetobacter baumannii (CRAB) is designated as an urgent public health threat, both due to its remarkable multidrug resistance and propensity for clonal spread. This study aimed to explore the phenotypic and molecular characteristics of antimicrobial resistance in CRAB isolates (n = [...] Read more.

Carbapenem-resistant Acinetobacter baumannii (CRAB) is designated as an urgent public health threat, both due to its remarkable multidrug resistance and propensity for clonal spread. This study aimed to explore the phenotypic and molecular characteristics of antimicrobial resistance in CRAB isolates (n = 73) from intensive care unit (ICU) patients in two university hospitals in Bulgaria (2018–2019). The methodology included antimicrobial susceptibility testing, PCR, whole-genome sequencing (WGS), and phylogenomic analysis. The resistance rates were as follows: imipenem, 100%; meropenem, 100%; amikacin, 98.6%; gentamicin, 89%; tobramycin, 86.3%; levofloxacin, 100%; trimethoprim–sulfamethoxazole, 75.3%; tigecycline, 86.3%; colistin, 0%; and ampicillin–sulbactam, 13.7%. All isolates harbored bla_OXA-51-like genes. The frequencies of distribution of other antimicrobial resistance genes (ARGs) were: bla_OXA-23-like, 98.6%; bla_{OXA-24/40-like}, 2.7%; armA, 86.3%; and sul1, 75.3%. The WGS of selected extensively drug-resistant A. baumannii (XDR-AB) isolates (n = 3) revealed the presence of OXA-23 and OXA-66 carbapenem-hydrolyzing class D β-lactamases in all isolates, and OXA-72 carbapenemase in one of them. Various insertion sequencies, such as ISAba24, ISAba31, ISAba125, ISVsa3, IS17, and IS6100, were also detected, providing increased ability for horizontal transfer of ARGs. The isolates belonged to the widespread high-risk sequence types ST2 (n = 2) and ST636 (n = 1) (Pasteur scheme). Our results show the presence of XDR-AB isolates, carrying a variety of ARGs, in Bulgarian ICU settings, which highlights the crucial need for nationwide surveillance, especially in the conditions of extensive antibiotic usage during COVID-19. Full article

(This article belongs to the Special Issue Antimicrobial Resistance in Non-Fermenting Gram-Negative Bacilli)

► Show Figures

Figure 1

Open AccessArticle

Predatory Strategies of Myxococcus xanthus: Prey Susceptibility to OMVs and Moonlighting Enzymes

by

,

,

,

and

Microorganisms 2023, 11(4), 874; https://doi.org/10.3390/microorganisms11040874 - 29 Mar 2023

Abstract

Predatory outer membrane vesicles (OMVs) secreted by myxobacteria fuse readily with the outer membranes of Gram-negative bacteria, introducing toxic cargo into their prey. Here we used a strain of the myxobacterium Myxococcus xanthus that produces fluorescent OMVs to assay the uptake of OMVs [...] Read more.

Predatory outer membrane vesicles (OMVs) secreted by myxobacteria fuse readily with the outer membranes of Gram-negative bacteria, introducing toxic cargo into their prey. Here we used a strain of the myxobacterium Myxococcus xanthus that produces fluorescent OMVs to assay the uptake of OMVs by a panel of Gram-negative bacteria. M. xanthus strains took up significantly less OMV material than the tested prey strains, suggesting that re-fusion of OMVs with producing organisms is somehow inhibited. The OMV killing activity against different prey correlated strongly with the predatory activity of myxobacterial cells, however, there was no correlation between OMV killing activity and their propensity to fuse with different prey. It has previously been proposed that M. xanthus GAPDH stimulates the predatory activity of OMVs by enhancing OMV fusion with prey cells. Therefore, we expressed and purified active fusion proteins of M. xanthus glyceraldehyde-3-phosphate dehydrogenase and phosphoglycerate kinase (GAPDH and PGK; moonlighting enzymes with additional activities beyond their roles in glycolysis/gluconeogenesis) to investigate any involvement in OMV-mediated predation. Neither GAPDH nor PGK caused lysis of prey cells or enhanced OMV-mediated lysis of prey cells. However, both enzymes were found to inhibit the growth of Escherichia coli, even in the absence of OMVs. Our results suggest that fusion efficiency is not a determinant of prey killing, but instead resistance to the cargo of OMVs and co-secreted enzymes dictates whether organisms can be preyed upon by myxobacteria. Full article

(This article belongs to the Section Molecular Microbiology and Immunology)

► Show Figures

Figure 1

Open AccessArticle

Antimicrobial Mechanism of Salt/Acid Solution on Microorganisms Isolated from Trimmed Young Coconut

by

Khemmapas Treesuwan

,

Wannee Jirapakkul

,

Sasitorn Tongchitpakdee

,

Vanee Chonhenchob

,

Warapa Mahakarnchanakul

and

Kullanart Tongkhao

Microorganisms 2023, 11(4), 873; https://doi.org/10.3390/microorganisms11040873 - 29 Mar 2023

Abstract

This study investigated the inhibitory activity of organic solutions containing 5, 10, 15, 20 and 30% (w/v) sodium chloride and citric acid solution and 15:10, 15:15, 15:20 and 15:30% (w/v) sodium chloride (NaCl) combined with citric acid (CA) solution [...] Read more.

This study investigated the inhibitory activity of organic solutions containing 5, 10, 15, 20 and 30% (w/v) sodium chloride and citric acid solution and 15:10, 15:15, 15:20 and 15:30% (w/v) sodium chloride (NaCl) combined with citric acid (CA) solution (salt/acid solution) for 10 min against microorganisms isolated from trimmed young coconut: Bacillus cereus, B. subtilis, Staphylococcus aureus, S. epidermidis, Enterobacter aerogenes, Serratia marcescens, Candida tropicalis, Lodderromyces elongisporus, Aspergillus aculeatus and Penicillium citrinum. Commercial antimicrobial agents such as potassium metabisulfite and sodium hypochlorite (NaOCl) were used as the controls. Results showed that 30% (w/v) NaCl solution displayed antimicrobial properties against all microorganisms, with s reduction range of 0.00–1.49 log CFU/mL. Treatment of 30% (w/v) CA solution inhibited all microorganisms in the reduction range of 1.50–8.43 log CFU/mL, while 15:20% (w/v) salt/acid solution was the minimum concentration that showed a similar antimicrobial effect with NaOCl and strong antimicrobial effect against Gram-negative bacteria. The mode of action of this solution against selected strains including B. cereus, E. aerogenes and C. tropicalis was also determined by scanning electron microscopy and transmission electron microscopy. B. cereus and E. aerogenes revealed degradation and detachment of the outer layer of the cell wall and cytoplasm membrane, while cytoplasmic inclusion in treated C. tropicalis cells changed to larger vacuoles and rough cell walls. The results suggested that a 15:20% (w/v) salt/acid solution could be used as an alternative antimicrobial agent to eliminate microorganisms on fresh produce. Full article

(This article belongs to the Special Issue Antimicrobial Compounds from Alternative Sources 2.0)

► Show Figures

Figure 1

Open AccessReview

Co-Occurrence of Taste and Odor Compounds and Cyanotoxins in Cyanobacterial Blooms: Emerging Risks to Human Health?

by

,

,

,

and

Microorganisms 2023, 11(4), 872; https://doi.org/10.3390/microorganisms11040872 - 28 Mar 2023

Abstract

Cyanobacteria commonly form large blooms in waterbodies; they can produce cyanotoxins, with toxic effects on humans and animals, and volatile compounds, causing bad tastes and odors (T&O) at naturally occurring low concentrations. Notwithstanding the large amount of literature on either cyanotoxins or T&O, [...] Read more.

Cyanobacteria commonly form large blooms in waterbodies; they can produce cyanotoxins, with toxic effects on humans and animals, and volatile compounds, causing bad tastes and odors (T&O) at naturally occurring low concentrations. Notwithstanding the large amount of literature on either cyanotoxins or T&O, no review has focused on them at the same time. The present review critically evaluates the recent literature on cyanotoxins and T&O compounds (geosmin, 2-methylisoborneol, β-ionone and β-cyclocitral) to identify research gaps on harmful exposure of humans and animals to both metabolite classes. T&O and cyanotoxins production can be due to the same or common to different cyanobacterial species/strains, with the additional possibility of T&O production by non-cyanobacterial species. The few environmental studies on the co-occurrence of these two groups of metabolites are not sufficient to understand if and how they can co-vary, or influence each other, perhaps stimulating cyanotoxin production. Therefore, T&Os cannot reliably serve as early warning surrogates for cyanotoxins. The scarce data on T&O toxicity seem to indicate a low health risk (but the inhalation of β-cyclocitral deserves more study). However, no data are available on the effects of combined exposure to mixtures of cyanotoxins and T&O compounds and to combinations of T&O compounds; therefore, whether the co-occurrence of cyanotoxins and T&O compounds is a health issue remains an open question. Full article

(This article belongs to the Special Issue Phototrophic Bacteria 2.0)

Open AccessEditorial

Special Issue: Beneficial Properties and Safety of Lactic Acid Bacteria

by

Wilhelm Heinrich Holzapfel

and

Svetoslav Dimitrov Todorov

Microorganisms 2023, 11(4), 871; https://doi.org/10.3390/microorganisms11040871 - 28 Mar 2023

Abstract

The application of LAB in various sectors, including in the biotechnical and food industry, in human and veterinary practice, and in health-promoting practices and cosmetics, has been the subject of intensive research across the globe, with a range of traditional and innovative methods [...] Read more.

The application of LAB in various sectors, including in the biotechnical and food industry, in human and veterinary practice, and in health-promoting practices and cosmetics, has been the subject of intensive research across the globe, with a range of traditional and innovative methods currently being explored [...] Full article

(This article belongs to the Special Issue Benefical Properties and Safety of Lactic Acid Bacteria)

Open AccessArticle

Genome-Wide Pathway Exploration of the Epidermidibacterium keratini EPI-7^T

by

,

,

,

,

and

Microorganisms 2023, 11(4), 870; https://doi.org/10.3390/microorganisms11040870 - 28 Mar 2023

Abstract

Functional cosmetics industries using skin microbiome screening and beneficial materials isolated from key microorganisms are receiving increasing attention. Since Epidermidibacterium keratini EPI-7^T was first discovered in human skin, previous studies have confirmed that it can produce a new pyrimidine compound, 1,1′-biuracil, having [...] Read more.

Functional cosmetics industries using skin microbiome screening and beneficial materials isolated from key microorganisms are receiving increasing attention. Since Epidermidibacterium keratini EPI-7^T was first discovered in human skin, previous studies have confirmed that it can produce a new pyrimidine compound, 1,1′-biuracil, having anti-aging effects on human skin. Therefore, we conducted genomic analyses to judge the use value of E. keratini EPI-7^T and provide up-to-date information. Whole-genome sequencing analysis of E. keratini EPI-7^T was performed to generate new complete genome and annotation information. E. keratini EPI-7^T genome was subjected to comparative genomic analysis with a group of closely-related strains and skin flora strains through bioinformatic analysis. Furthermore, based on annotation information, we explored metabolic pathways for valuable substances that can be used in functional cosmetics. In this study, the whole-genome sequencing (WGS) and annotation results of E. keratini EPI-7^T were improved, and through comparative analysis, it was confirmed that the E. keratini EPI-7^T has more metabolite-related genes than comparison strains. In addition, we annotated the vital genes for biosynthesis of 20 amino acids, orotic acid, riboflavin (B2) and chorismate. In particular, we were able to prospect that orotic acid could accumulate inside E. keratini EPI-7^T under uracil-enriched conditions. Therefore, through a genomics approach, this study aims to provide genetic information for the hidden potential of E. keratini EPI-7^T and the strain development and biotechnology utilization to be conducted in further studies. Full article

(This article belongs to the Section Microbial Biotechnology)

► Show Figures

Figure 1

Journal Description

Microorganisms

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI