Dear Colleagues,

Nontuberculous mycobacteria (NTM) species, which are the causative agents of serious mycobacteriosis, and whose sources in the environment have not yet been identified, remain an epidemiological phenomenon. In addition to water and water biofilm, other habitats of the environment (water sediments, soil, dust, etc.) can also be considered sources of mycobacterioses. For some causative agents of mycobacteriosis (e.g., Mycobacterium avium, M. chimaera, M. malmoense, M. xenopi, M. abscessus, and M. fortuitum), their occurrence, ecology, and transmission pathways have been described. For the causative agent of Buruli Ulcer, the occurrence and exposure risks of M. ulcerans are currently being intensively researched with partial success. For many other NTM species causing pulmonary and extrapulmonary mycobacterioses (M. setense, etc.), the sources are still completely unknown.

In the last two decades, much attention has been paid to the occurrence of NTM in various environmental habitats. Examples include research on NTM in household and hospital plumbing, soil, peat, garden substrates or fertilizers containing bird and bat guano. All these substances are intensively colonized by NTM. There is still only fragmentary information about the ecological significance of NTM. At the same time, these matrices, in addition to water and biofilm, are most likely of crucial importance in the spread of various types of NTM. In many countries, the widespread vaccination of children with the BCG vaccine against human tuberculosis has been stopped. This has opened up the scope for NTM. Therefore, research in solid matrices (dust, soil, peat, and others) has not only ecological but also health significance. Different types of NTM occurring in environmental components can play an important ecological role under certain circumstances.

The role of NTM in the environment is also gaining importance from the point of view of the degradation of various contaminating substances, e.g., organic pollutants, neonicotinoids, atrazine, and polycyclic aromatic hydrocarbons (PAH). Currently, NTM have been isolated from tomato plant roots and in pitcher plants growing in sphagnum peat bogs. A wide spectrum of NTM species has been detected in bat guano, in natural peat bogs, in garden peat, and in garden substrates. NTM are also capable of internalization into plant tissues. All these results indicate that the role of NTM in the environment is not yet sufficiently revealed.

Therefore, the aim of this Special Issue of Microorganisms is to present a collection of articles that provide a current view of the research in the NTM epidemiology and ecology. Manuscripts covering all aspects of research relating to NTM sources, clinical relevance, and ecology are welcome.

Prof. Dr. Ivo Pavlík
Prof. Dr. Joseph Oliver Falkinham
Prof. Dr. Roger Pickup
Guest Editors

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• molecular ecology of mycobacterioses
• new diagnostic approaches
• ecology of nontuberculous mycobacteria
• soil-borne mycobacterioses
• colonized water sediments and biofilms by mycobacteria
• peat and garden substrates inhabited by mycobacteria