Editorial

3 pages, 187 KiB

Open AccessEditorial

Special Issue “Biotechnological Application of Photosynthetic Bacteria”

by Hitoshi Miyasaka

Microorganisms 2023, 11(3), 619; https://doi.org/10.3390/microorganisms11030619 - 28 Feb 2023

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This Special Issue aims to contribute to the current knowledge in the field and promote the practical application of photosynthetic bacteria (PSB) biotechnology [...] Full article

(This article belongs to the Special Issue Biotechnological Application of Photosynthetic Bacteria)

Research

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14 pages, 2573 KiB

Open AccessArticle

Probiotic Effects of a Marine Purple Non-Sulfur Bacterium, Rhodovulum sulfidophilum KKMI01, on Kuruma Shrimp (Marsupenaeus japonicus)

by Aoi Koga, Midori Goto, Shuhei Hayashi, Shinjiro Yamamoto and Hitoshi Miyasaka

Microorganisms 2022, 10(2), 244; https://doi.org/10.3390/microorganisms10020244 - 22 Jan 2022

Cited by 11 | Viewed by 3524

Abstract

Purple non-sulfur bacteria (PNSB) are used as probiotics in shrimp aquaculture; however, no studies have examined the probiotic effects of PNSB in shrimp at the gene expression level. In this study, we examined the effects of a marine PNSB, Rhodovulum sulfidophilum KKMI01, on [...] Read more.

Purple non-sulfur bacteria (PNSB) are used as probiotics in shrimp aquaculture; however, no studies have examined the probiotic effects of PNSB in shrimp at the gene expression level. In this study, we examined the effects of a marine PNSB, Rhodovulum sulfidophilum KKMI01, on the gene expression of kuruma shrimp (Marsupenaeus japonicus). Short-term (3 days) effects of R. sulfidophilum KKMI01 on the gene expression in shrimp were examined using small-scale laboratory aquaria experiments, while long-term (145 days) effects of R. sulfidophilum KKMI01 on the growth performance and gene expression were examined using 200-ton outdoor aquaria experiments. Gene expression levels were examined using qRT-PCR. Results of the short-term experiments showed the upregulation of several molting-related genes, including cuticle proteins, calcification proteins, and cuticle pigment protein, suggesting that PNSB stimulated the growth of shrimp. The upregulation of several immune genes, such as prophenoloxidase, antimicrobial peptides, and superoxide dismutase, was also observed. In the 145-day outdoor experiments, the average body weight at harvest time, survival rate, and feed conversion ratio were significantly improved in PNSB-treated shrimp, and upregulation of molting and immune-related genes were also observed. When PNSB cells were added to the rearing water, the effective dosage of PNSB was as low as 10³ cfu/mL, which was more than a million times dilution of the original PNSB culture (2–3 × 10⁹ cfu/mL), indicating that R. sulfidophilum KKMI01 provides a feasible and cost-effective application as a probiotic candidate in shrimp aquaculture. Full article

(This article belongs to the Special Issue Biotechnological Application of Photosynthetic Bacteria)

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16 pages, 3594 KiB

Open AccessArticle

Effects of Mixing Volatile Fatty Acids as Carbon Sources on Rhodospirillum rubrum Carbon Metabolism and Redox Balance Mechanisms

by Paloma Cabecas Segura, Quentin De Meur, Audrey Tanghe, Rob Onderwater, Laurent Dewasme, Ruddy Wattiez and Baptiste Leroy

Microorganisms 2021, 9(9), 1996; https://doi.org/10.3390/microorganisms9091996 - 21 Sep 2021

Cited by 8 | Viewed by 2206

Abstract

Rhodospirillum rubrum has a versatile metabolism, and as such can assimilate a broad range of carbon sources, including volatile fatty acids. These carbon sources are gaining increasing interest for biotechnological processes, since they reduce the production costs for numerous value-added compounds and contribute [...] Read more.

Rhodospirillum rubrum has a versatile metabolism, and as such can assimilate a broad range of carbon sources, including volatile fatty acids. These carbon sources are gaining increasing interest for biotechnological processes, since they reduce the production costs for numerous value-added compounds and contribute to the development of a more circular economy. Usually, studies characterizing carbon metabolism are performed by supplying a single carbon source; however, in both environmental and engineered conditions, cells would rather grow on mixtures of volatile fatty acids (VFAs) generated via anaerobic fermentation. In this study, we show that the use of a mixture of VFAs as carbon source appears to have a synergy effect on growth phenotype. In addition, while propionate and butyrate assimilation in Rs. rubrum is known to require an excess of bicarbonate in the culture medium, mixing them reduces the requirement for bicarbonate supplementation. The fixation of CO₂ is one of the main electron sinks in purple bacteria; therefore, this observation suggests an adaptation of both metabolic pathways used for the assimilation of these VFAs and redox homeostasis mechanism. Based on proteomic data, modification of the propionate assimilation pathway seems to occur with a switch from a methylmalonyl-CoA intermediate to the methylcitrate cycle. Moreover, it seems that the presence of a mixture of VFAs switches electron sinking from CO₂ fixation to H₂ and isoleucine production. Full article

(This article belongs to the Special Issue Biotechnological Application of Photosynthetic Bacteria)

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10 pages, 3100 KiB

Open AccessArticle

Comparative Genome Analysis Provides Molecular Evidence for Reclassification of the Photosynthetic Bacterium Rhodobacter sphaeroides EBL0706 as a Strain of Luteovulum azotoformans

by Haoyu Wang, Xiaoling Sha, Rui Li, Yijing Li, Himel Nahreen Khaleque, Yuxiu Zhang, Tsing Bohu, Zhihui Bai and Xuliang Zhuang

Microorganisms 2021, 9(8), 1754; https://doi.org/10.3390/microorganisms9081754 - 17 Aug 2021

Cited by 3 | Viewed by 2445

Abstract

In this study, we conducted a genome-wide comparative analysis of a former Rhodobacter sphaeroides strain EBL0706, which is now recorded as Luteovulum sphaeroides EBL0706. The genome of EBL0706 was compared with that of Luteovulum azotoformans ATCC 17025, Luteovulum azotoformans KA25, and Luteovulum sphaeroides [...] Read more.

In this study, we conducted a genome-wide comparative analysis of a former Rhodobacter sphaeroides strain EBL0706, which is now recorded as Luteovulum sphaeroides EBL0706. The genome of EBL0706 was compared with that of Luteovulum azotoformans ATCC 17025, Luteovulum azotoformans KA25, and Luteovulum sphaeroides 2.4.1. The average nucleotide identity (ANI), tetra nucleotide signatures (Tetra), digital DNA–DNA hybridization (dDDH) values, comparative genome, and phylogenetic analysis proposed that EBL0706 is a strain of Luteovulum azotoformans. Functional annotations identified a total of 4034 protein-coding genes in the genome of EBL0706, including a complete photosynthetic gene cluster. This study provides genomic molecular verification for the strain EBL0706 to be reclassified to Luteovulum azotoformans. Full article

(This article belongs to the Special Issue Biotechnological Application of Photosynthetic Bacteria)

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8 pages, 1285 KiB

Open AccessCommunication

Assessment of Voltage Influence in Carbon Dioxide Fixation Process by a Photo-Bioelectrochemical System under Photoheterotrophy

by Sara Díaz-Rullo Edreira, Silvia Barba, Ioanna A. Vasiliadou, Raúl Molina, Juan Antonio Melero, Juan José Espada, Daniel Puyol and Fernando Martínez

Microorganisms 2021, 9(3), 474; https://doi.org/10.3390/microorganisms9030474 - 25 Feb 2021

Cited by 6 | Viewed by 2422

Abstract

Bioelectrochemical systems are a promising technology capable of reducing CO₂ emissions, a renewable carbon source, using electroactive microorganisms for this purpose. Purple Phototrophic Bacteria (PPB) use their versatile metabolism to uptake external electrons from an electrode to fix CO₂. In [...] Read more.

Bioelectrochemical systems are a promising technology capable of reducing CO₂ emissions, a renewable carbon source, using electroactive microorganisms for this purpose. Purple Phototrophic Bacteria (PPB) use their versatile metabolism to uptake external electrons from an electrode to fix CO₂. In this work, the effect of the voltage (from −0.2 to −0.8 V vs. Ag/AgCl) on the metabolic CO₂ fixation of a mixed culture of PPB under photoheterotrophic conditions during the oxidation of a biodegradable carbon source is demonstrated. The minimum voltage to fix CO₂ was between −0.2 and −0.4 V. The Calvin–Benson–Bassham (CBB) cycle is the main electron sink at these voltages. However, lower voltages caused the decrease in the current intensity, reaching a minimum at −0.8 V (−4.75 mA). There was also a significant relationship between the soluble carbon uptake in terms of chemical oxygen demand and the electron consumption for the experiments performed at −0.6 and −0.8 V. These results indicate that the CBB cycle is not the only electron sink and some photoheterotrophic metabolic pathways are also being affected under electrochemical conditions. This behavior has not been tested before in photoheterotrophic conditions and paves the way for the future development of photobioelectrochemical systems under heterotrophic conditions. Full article

(This article belongs to the Special Issue Biotechnological Application of Photosynthetic Bacteria)

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Review

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21 pages, 1953 KiB

Open AccessReview

Potential of Phototrophic Purple Nonsulfur Bacteria to Fix Nitrogen in Rice Fields

by Isamu Maeda

Microorganisms 2022, 10(1), 28; https://doi.org/10.3390/microorganisms10010028 - 24 Dec 2021

Cited by 17 | Viewed by 4685

Abstract

Biological nitrogen fixation catalyzed by Mo-nitrogenase of symbiotic diazotrophs has attracted interest because its potential to supply plant-available nitrogen offers an alternative way of using chemical fertilizers for sustainable agriculture. Phototrophic purple nonsulfur bacteria (PNSB) diazotrophically grow under light anaerobic conditions and can [...] Read more.

Biological nitrogen fixation catalyzed by Mo-nitrogenase of symbiotic diazotrophs has attracted interest because its potential to supply plant-available nitrogen offers an alternative way of using chemical fertilizers for sustainable agriculture. Phototrophic purple nonsulfur bacteria (PNSB) diazotrophically grow under light anaerobic conditions and can be isolated from photic and microaerobic zones of rice fields. Therefore, PNSB as asymbiotic diazotrophs contribute to nitrogen fixation in rice fields. An attempt to measure nitrogen in the oxidized surface layer of paddy soil estimates that approximately 6–8 kg N/ha/year might be accumulated by phototrophic microorganisms. Species of PNSB possess one of or both alternative nitrogenases, V-nitrogenase and Fe-nitrogenase, which are found in asymbiotic diazotrophs, in addition to Mo-nitrogenase. The regulatory networks control nitrogenase activity in response to ammonium, molecular oxygen, and light irradiation. Laboratory and field studies have revealed effectiveness of PNSB inoculation to rice cultures on increases of nitrogen gain, plant growth, and/or grain yield. In this review, properties of the nitrogenase isozymes and regulation of nitrogenase activities in PNSB are described, and research challenges and potential of PNSB inoculation to rice cultures are discussed from a viewpoint of their applications as nitrogen biofertilizer. Full article

(This article belongs to the Special Issue Biotechnological Application of Photosynthetic Bacteria)

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23 pages, 2525 KiB

Open AccessReview

From Lab to Farm: Elucidating the Beneficial Roles of Photosynthetic Bacteria in Sustainable Agriculture

by Sook-Kuan Lee, Huu-Sheng Lur and Chi-Te Liu

Microorganisms 2021, 9(12), 2453; https://doi.org/10.3390/microorganisms9122453 - 28 Nov 2021

Cited by 22 | Viewed by 8531

Abstract

Photosynthetic bacteria (PSB) possess versatile metabolic abilities and are widely applied in environmental bioremediation, bioenergy production and agriculture. In this review, we summarize examples of purple non-sulfur bacteria (PNSB) through biofertilization, biostimulation and biocontrol mechanisms to promote plant growth. They include improvement of [...] Read more.

Photosynthetic bacteria (PSB) possess versatile metabolic abilities and are widely applied in environmental bioremediation, bioenergy production and agriculture. In this review, we summarize examples of purple non-sulfur bacteria (PNSB) through biofertilization, biostimulation and biocontrol mechanisms to promote plant growth. They include improvement of nutrient acquisition, production of phytohormones, induction of immune system responses, interaction with resident microbial community. It has also been reported that PNSB can produce an endogenous 5-aminolevulinic acid (5-ALA) to alleviate abiotic stress in plants. Under biotic stress, these bacteria can trigger induced systemic resistance (ISR) of plants against pathogens. The nutrient elements in soil are significantly increased by PNSB inoculation, thus improving fertility. We share experiences of researching and developing an elite PNSB inoculant (Rhodopseudomonas palustris PS3), including strategies for screening and verifying beneficial bacteria as well as the establishment of optimal fermentation and formulation processes for commercialization. The effectiveness of PS3 inoculants for various crops under field conditions, including conventional and organic farming, is presented. We also discuss the underlying plant growth-promoting mechanisms of this bacterium from both microbial and plant viewpoints. This review improves our understanding of the application of PNSB in sustainable crop production and could inspire the development of diverse inoculants to overcome the changes in agricultural environments created by climate change. Full article

(This article belongs to the Special Issue Biotechnological Application of Photosynthetic Bacteria)

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Other

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9 pages, 2022 KiB

Open AccessBrief Report

Plant-Growth-Promoting Effect by Cell Components of Purple Non-Sulfur Photosynthetic Bacteria

by Shuhei Hayashi, Yasunari Iwamoto, Yuki Hirakawa, Koichi Mori, Naoki Yamada, Takaaki Maki, Shinjiro Yamamoto and Hitoshi Miyasaka

Microorganisms 2022, 10(4), 771; https://doi.org/10.3390/microorganisms10040771 - 02 Apr 2022

Cited by 4 | Viewed by 2934

Abstract

Rhodobacter sphaeroides, a purple non-sulfur photosynthetic bacterium (PNSB), was disrupted by sonication and fractionated by centrifugation into the supernatant and pellet. The effects of the supernatant and pellet on plant growth were examined using Brassica rapa var. perviridis (komatsuna) in the pot [...] Read more.

Rhodobacter sphaeroides, a purple non-sulfur photosynthetic bacterium (PNSB), was disrupted by sonication and fractionated by centrifugation into the supernatant and pellet. The effects of the supernatant and pellet on plant growth were examined using Brassica rapa var. perviridis (komatsuna) in the pot experiments. Both fractions showed growth-promoting effects: the supernatant at high concentrations (1 × 10⁷ to 4 × 10⁷ cfu-equivalent mL⁻¹) and the pellet at a low concentration of 2 × 10³ cfu-equivalent mL⁻¹). We expected lipopolysaccharide (LPS) to be the active principle of the pellet fraction and examined the effects of LPS on the growth of B. rapa var. perviridis. The growth of the plants was significantly enhanced by the foliar feeding of R. sphaeroides LPS at concentrations ranging from 10 to 100 pg mL⁻¹. The present study is the first report indicating that LPS acts as one of the active principles of the plant-growth-promoting effect of PNSB. Full article

(This article belongs to the Special Issue Biotechnological Application of Photosynthetic Bacteria)

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