Infectious diseases, such as lactococcosis caused by Lactococcus garvieae, are portrayed as critical limiting factors in aquaculture. The antimicrobial properties of Lactic Acid Bacteria (LAB), mainly the production of organic acids and bacteriocins (e. g., the lanthionine containing nisins A and Z; NisA and NisZ, respectively), led to propose LAB as probiotics to be used as an alternative and/or complementary strategy to vaccination and chemotherapy in aquaculture. L. lactis RBT18, isolated from cultured rainbow trout, exerts a strong direct and extracellular antimicrobial activity against L. garvieae and other ichthyopathogens, being the latter heat-resistant (100ºC, 10 min), and thus suggesting the involvement of a thermostable antimicrobial compound (i. e., bacteriocin). Cross-immunity tests using the agar-well-diffusion test (ADT) and PCR assays suggested that NisA/Z is the bacteriocin responsible for the extracellular antimicrobial activity exerted by L. lactis RBT18. To demonstrate this hypothesis, the bacteriocin was purified to homogeneity by two multi-chromatographic procedures. MALDI TOF-MS analyses of purified samples after the last reverse-phase chromatography step identified the presence of NisZ (3,330 Da), and its oxidized form (3,346 Da), derived from the oxidation of a lanthionine ring. The oxidized NisZ showed a diminished antimicrobial activity which would increase the chances of bacterial pathogens to evade its antimicrobial activity. Further experiments are necessary to assess the in vitro and in vivo safety and efficiency of L. lactis RBT18 as probiotic in aquaculture, but also to optimize the environmental conditions to reduce bacteriocin oxidation and thus bacterial pathogen resistance.

The growth of the world's population sets the task of providing people with quality food. Getting a high yield of plants is impossible without the use of fertilizers and plant protection products. However, the use of a large number of chemical compounds leads to their excessive accumulation in plants and can have a negative impact on human health. On the other hand, compounds used for multidirectional treatment of plants partially enter the soil, penetrate into the groundwater, which ultimately affects the quality of natural waters and bottom sediments. Therefore, the primary task is to intensify agricultural production without causing additional damage to the environment. This problem can be partially solved using microorganisms with target properties. For example, microorganisms that increase the bioavailability of nutrients that have phytostimulating properties, have antifungal, insecticidal, acaricidal effects and, at the same time, decompose pesticide residues. Microorganisms that combine several useful traits are especially valuable.

Thphe aim of this work was to search for new microbial strains that are applicable for agricultural production and possess a complex technologically significant potential.

30 strains of soil organisms were isolated from soil samples of the central chernozem region of Russia. The primary selection of strains was performed by direct plating on an agar mineral medium containing sodium benzoate as the only source of carbon and energy. We proceeded from the assumption that the ability to degrade benzoate can serve as a criterion for the presence of a minimum biodegradative potential for two reasons. Despite the relatively simple structure of the benzoate molecule, the biodegradation of this compound presupposes the presence of specialized biodegradation pathways and genes. Bacterial strains capable of degrading benzoate are, to varying degrees, capable of degrading other pollutants. It is important to emphasize that the isolation of soil microorganisms on a mineral medium with benzoate made it possible to quickly assess the presence of one of two biodegradative pathways - ortho- or meta-cleavage of catechol. The data obtained did not allow us to detect strains decomposing benzoate via the pathway of meta-cleavage, since there was no yellow coloration of the medium, characteristic of 2-hydroxymuconic semialdehyde formed as a result of meta-cleavage of catechol, a product of benzoate biodegradation. Thus, it was shown that the metabolism of benzoate in the isolated strains occurs with the induction of catechol 1,2-dioxygenase.

Some of the isolated strains showed high antagonistic activity against fungi-phytopathogens. The new Pseudomonas strain showed high activity. This strain completely inhibited the growth of the fungus Fusarium graminearum, preventing the phytopathogen from developing within a month of co-cultivation. The ability of this strain to inhibit the growth of the bacterial phytopathogen Ralstonia sp. 7-1 should be specially noted. Thus, a number of bacterial strains have been identified that are promising for use in plant protection technologies.

Among the highlighted ones, a new bacterial strain Bacillus sp. This strain is a spore-forming culture and is distinguished by an unusual morphology and development cycle of gram-positive cells. During growth, the strain forms chains of cells of irregular shape, which on the first day of growth on rich nutrient media are filled with multiple lipid granules of unknown nature. Of particular interest is the ability of one of the cells in the chain to divide, forming a helical cell form, which is further split into multiple small irregular cell forms.

Thus, the study of the microbial diversity of chernozems made it possible to identify strains potentially significant for biotechnology, combining such important properties as activity against phytopathogens and decomposition of pollutants, which makes it possible to develop biopreparations for multipurpose purposes. In addition, the isolation of new, previously undescribed bacteria significantly expands the understanding of microbial biodiversity.

The reported study was funded by RFBR according to the research project № 19-54-80003.

Shiga toxin (Stx)-producing Escherichia coli strains are foodborne pathogens that can cause severe human diseases, such as haemorrhagic colitis and haemolytic-uraemic syndrome. Stxs are encoded by bacteriophages (Stx phages) which show remarkable variations in genome composition and harbour several genes of unknown function. Recently, a gene encoding a sialate O-acetylesterase (NanS-p) was identified in some relevant Stx2a phages and it was suggested that it could provide advantages for bacterial growth in the gut. The aim of this study was to analyze the presence and sequence of nanS-p genes in available Stx2a genomes. A total of 59 DNA sequences of Stx2a phages were extracted from NCBI GenBank database with the BLASTN program using the stx_2a sequence from the phage 933W as query sequence, either as complete phage genomes (45) or from bacterial genomes by subsequent analysis with PHASTER web server (14). Comparative analysis revealed that nanS-p was located downsteam stx_2a in all genomes. Twenty different amino acid sequences of NanS-p were identified among the 59 Stx2a phages. Specifically, catalytic esterase domains were clustered in 11 groups, with differences mainly observed in nine amino acid positions. Sequences corresponding to the N-terminal domain (DUF1737) clustered into three groups, two of them closely related, while C-terminal domain was highly variable giving place to four groups. Since sialate O-acetylesterase activity has been determined from particular Stx2a phages, new studies are necessary to evaluate if the NanS-p subtypes identified in the present study also differ in their biological activity.

The human pathogen of Mycobacterium tuberculosis (MTB) is indeed one of the renowned important longtime infectious diseases, tuberculosis (TB). Interestingly, MTB infection has become one of the world's leading causes of human death. In trehalose synthase, the protein NCGM 946K2 146 found in MTB has an important role. For carbohydrate transport and metabolism, trehalose synthase is required. The protein isn't clarified yet, though. In this research, an in silico approach was therefore formulated for functional and structural documentation of the uncharacterized protein NCGM946K2 146.Three distinct servers, including Modeller, Phyre2, and Swiss Model were used to evaluate the predicted tertiary structure. The top materials are selected using structural evaluations conducted with the analysis of Ramachandran Plot, Swiss-Model Interactive Workplace, Prosa-web, Verify 3D, and Z scores. This analysis aimed to uncover the value of the NCGM946K2 146 protein of MTB. This research will, therefore, improve our pathogenesis awareness and give us a chance to target the protein compound.

Introduction. Anaerobic digestion (AD) is considered one of the most beneficial technologies for the treatment of organic wastes, from which energy in form of biogas and digestate as a soil amendment can be obtained. However, AD often suffers from process instability due to high levels of inorganic toxic substances such as ammonium, phosphates, sulfates or metal ions, variations in operating parameters such as temperature and pH, as well as a lack of proper balance between microbial groups. One of the alternatives to combat these imbalances is bioaugmentation, which is defined as the addition of specific microorganisms (either pure cultures or microbial consortia) into the system to accomplish a certain function. In this work, hydrogenotrophic methanogens were used to improve the methane yield of a thermophilic AD process of the organic fraction of municipal solid wastes (OFMSW) in Mexico City. Methods. The OFMSW (substrate) and leachate (inoculum) were collected from a composting plant in Mexico City. The consortium containing the hydrogenotrophic methanogens was isolated from the leachate. A biochemical methane potential (BMP) test was performed to know if the consortium influenced the methane yield. A 1:1 volatile solids (VS) ratio substrate/inoculum was operated in 125 mL serum bottles with a working volume of 60 ml. The consortium was added to different volume ratios. The process lasted 32 days at 55° C and 60 rpm. The identification of the microbial communities of all treatment groups and consortium were done by high throughput DNA sequencing of bacterial and archaeal 16S rDNA libraries. Results. The highest yield >600 ml CH₄/g VS_added was achieved when 25% of the consortium was added followed by 50%; however, between these two treatments, there was not a statistically significant difference. The rest of the treatments were under 600 ml CH₄/g VS_added. Nevertheless, it should be noted that the treatment at 25% reached its methane peak after 10 days, meanwhile, the treatment at 50% reached it on approximately 8 days, suggesting in this last treatment, the generation of methane was more accelerated. The methane yield increased by approximately 7% and 5% compared to the control (0%), while using 25% and 50% of the consortium, respectively. Regarding the bacterial communities, it was found that the consortium was mainly composed of members of the phylum Synergistetes. Members of this phylum are known for their acetate oxidizing properties. In all the treatments the phyla Firmicutes, Thermotogae, and Synergistetes were dominant and as the concentration of the consortium in the treatments increased, the presence of the family Thermotogaceae also increased. Conclusions. In this research, we detected that the bioaugmentation using hydrogenotrophic methanogens improved the methane yield of the AD process by more than 5%. The bacterial communities present in the consortium have capacities to degrade cellulolytic compounds and act as acetate oxidants, which play a role in syntrophy with hydrogenotrophic methanogens, however, it is still necessary to know the dynamics of the methanogens. Acknowledgments. The project was supported by CIIEMAD IPN SIP 20172277, 20180942, 20195607, and CONACyT-163235 INFR-2011-01. AKGB was granted a CONACyT-700337 doctorate scholarship.