Fems Microbiology Letters最新文献

Aerobic chemoorganotrophic planctomycetes of the genus Schlesneria colonize a wide spectrum of freshwater ecosystems. The only described species of this genus, S. paludicola, is represented by ellipsoid-shaped, moderately acidophilic bacteria isolated from acidic peat bogs. Here, we characterize a novel neutrophilic member of this genus from a mountain wetland, strain T3-172T. This isolate possesses unpigmented, non-motile, spherical cells, which grow on media containing some mono- and polysaccharides in the pH range of 6.0-7.5 and at temperatures between 15 and 37°C. Good growth is observed on xylan, one of the major plant cell wall biopolymers. The genome of strain T3-172T is 7.16 Mb in size and contains two unlinked sets of rRNA genes, 93 tRNA genes, and about 5500 potential protein-coding genes. Among the latter, the GH5 family protein is identified as the most reliable candidate for the cleavage of xylan. The 16S rRNA gene sequence of strain T3-172T displays 97.8% similarity to that of S. paludicola MPL7T, and the average nucleotide identity between the genomes of these planctomycetes is 71.6%. We, therefore, propose a novel species of the genus Schlesneria, S. sphaerica sp. nov., with strain T3-172T (=KCTC 102306T = VKM B-3856T) as the type strain.

Chronological lifespan (CLS) in budding yeast Saccharomyces cerevisiae, which is defined as the time nondividing cells in saturation remain viable, has been utilized as a model to study post-mitotic aging in mammalian cells. CLS is closely related to entry into and maintenance of a quiescent state. Many rearrangements that direct the quiescent state enhance the ability of cells to endure several types of stress. Small ubiquitin-like modifier (SUMO)-targeted ubiquitin ligases (STUbLs) play a critical role in mediating an adaptive response to various stresses. In this study, we investigated the effect of a STUbL, Slx5/Slx8, on CLS in budding yeast. We showed that both SLX5 and SLX8 deletions accelerate chronological aging, resulting in a decreased maximum and mean lifespan. slx5Δ cells were capable of entering or maintaining a quiescent state during aging. On the other hand, aging slx5Δ and slx8Δ cells had both increased spontaneous mutation accumulation. Our data together indicate that Slx5/Slx8 STUbL is required for normal rate of aging by preventing increased spontaneous mutation accumulation during aging.

A new filamentous phototrophic bacterium Khr17 was isolated as an enrichment culture from the brackish polar lake Bol'shie Khruslomeny. The organism was a halotolerant, strictly anaerobic phototroph possessing photosystem II. Sulfide was required for phototrophic growth. The cells of bacterium Khr17 formed nonmotile, wavy trichomes surrounded by a sheath. The cells contained chlorosomes, gas vesicles, and storage granules. The antenna pigments of bacterium Khr17 were bacteriochlorophyll c and β- and γ-carotenes. The genome of Khr17 bacterium carries all the genes responsible for CO2 fixation via the 3-hydroxypropionate pathway. The genes encoding the proteins of the nitrogenase complex were not found. The DNA G + C content was 59.9%. The 16S rRNA gene sequence of isolate Khr17 exhibited 99.4% similarity to related species. The average nucleotide identity and digital DNA-DNA hybridization values for the isolate showed 91.9% and 46.9% similarity, respectively, to other 'Ca. Chloroploca' species. Based on its phenotypic and phylogenetic characteristics, classification of Khr17 as member of a new species, 'Ca. Chloroploca septentrionalis' sp. nov., was proposed. Members of the genus 'Ca. Chloroploca' have previously not been found in Arctic areas and in the plankton of meromictic lakes.

Chloroacetamide herbicides are widely used to control weeds globally. In this study, three acetochlor-degrading mixed cultures using nitrate, sulfate, and ferric iron as electron acceptors were isolated and determined for their degradation under anaerobic conditions. The degradation rates of all mixed pure cultures in a mineral medium were not much different at 1 µM, while the rates at 50 µM were in the order: mixed culture using nitrate > sulfate > ferric iron as electron acceptors, giving 6.70, 6.13, and 4.85 µM/day, respectively. During acetochlor degradation, 2-ethyl-6-methyl-N-(ethoxymethyl)acetanilide, N-2-ethylphenyl acetamide, and 2-ethylaniline were transiently produced. Interestingly, the mixture of all cultures synergistically degraded pretilachlor although no individual strains could degrade the compound. Toluene and 2-ethylaniline were metabolites of pretilachlor degradation by the acetochlor-degrading bacteria. However, pretilachlor inhibited the acetochlor degradation by acetochlor-degrading bacteria. The inoculation of both acetochlor- and pretilachlor-degrading bacteria resulted in 91.4 ± 2.1% of acetochlor and 82.4 ± 2.6% of pretilachlor being utilized for 7 days. Moreover, the introduction of these degrading bacteria accelerated the degradation of both substrates contaminating water and sediment collected from a pond. This study provides insights into anaerobic degradation by pure cultures using different electron acceptors.

Latilactobacillus curvatus, found in various fermented foods, is a promising probiotic with unique health benefits. Lipoteichoic acid (LTA) is a characteristic amphiphilic surface polymer of Gram-positive bacteria and exhibits immunomodulatory activities. Despite the structural diversity of LTA among different bacterial species and strains, no information is available on the chemical structure of LTA in L. curvatus. In this study, we aimed to determine the structure of LTA isolated from L. curvatus CP2998. One- and two-dimensional nuclear magnetic resonance spectra of intact LTA revealed that LTA had a glycerolphosphate polymer as a hydrophilic main chain with partial substitutions of α-linked glucose and d-alanine at the hydroxy group at position 2 of the glycerol residue. The anchor glycolipid fraction was obtained by hydrofluoric acid treatment. Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry spectrum of the anchor glycolipid revealed that it contained diglucosyldiacylglycerol and diglucosylmonoacylglycerol. Our results suggest that L. curvatus CP2998 possesses a typical type I LTA structure; however, the lactic acid bacteria-specific anchor glycolipid structures, such as tri- or tetra-saccharides and three fatty acid residues, were not identified.

Fungi from the genus Dekkera, also known as Brettanomyces, are significant contaminants in commercial beer and wine production, and when present unintentionally, these non-domesticated yeasts result in the development of undesirable sensorial characteristics, in part due to the production of volatile phenols and acetate esters. The persistence of Dekkera spp. in industrial manufacturing environments can be attributed to its strong bioadhesive properties, allowing it to attach to various surfaces and form biofilms, which often contribute to recurrent contaminations. In other fungi, the yeast-to-filamentous transition is pivotal in enhancing bioadhesive properties, a process tightly regulated by density-dependent quorum-sensing mechanisms. However, there is no documented evidence regarding the influence of fungal quorum-sensing compounds on the yeast-to-filamentous transition in Dekkera, nor is there any evidence of existing quorum-sensing circuits in this genus. In this investigation, two Dekkera spp. were cultivated on a modified nitrogen-limiting synthetic low-ammonium dextrose medium supplemented with exogenous concentrations of quorum-sensing molecules 2-phenylethanol and tryptophol. Following cultivation, whole colonies were imaged and analyzed with a whole colony filamentation algorithm to quantify their filamentation. Our results demonstrate that the quorum-sensing compounds 2-phenylethanol and tryptophol significantly promote the yeast-to-filamentous transition in Dekkera spp., underscoring the broader presence of quorum-regulated social behaviors within this genus.

Micromonospora carbonacea JXNU-1, a strain of an actinomycete with broad-spectrum antimicrobial activity, isolated from soil samples from the farmland in the area of Yaohu Lake in Nanchang, China, was taken as the object of study in this paper. Bioinformatics analysis revealed that there was a pair of proteins MCNtrB/MCNtrC homologous to the two-component system NtrB/NtrC, which usually exists only in the Gram-negative bacteria and is closely related to the regulation of nitrogen metabolism, in the whole cell protein of M. carbonacea. MCNtrB and MCNtrC, obtained by expression in vitro, were subjected to autophosphorylation and phosphate group transfer experiments. The results showed that MCNtrB had histidine kinase activity with the active site of His115, and MCNtrC can accept the phosphate group from phosphorylated MCNtrB with the active site of Asp33. The yeast two-hybrid experiments showed that MCNtrB and MCNtrC were a pair of proteins with a strong interaction. Overexpression of MCNtrB and MCNtrC in M. carbonacea can affect the expression of key enzymes in cellular nitrogen metabolism, such as glutamine synthetase, glutamate synthase, and glutamate dehydrogenase. These results indicated that MCNtrB/MCNtrC is a two-component system related to nitrogen metabolism in M. carbonacea, which could provide an important experimental basis for revealing the regulatory mechanism of nitrogen metabolism in M. carbonacea.