Fems Microbiology Letters最新文献

Bentonite clay is an important component of deep geological repositories for long-term storage of used nuclear fuel. Studying the microbiology of bentonite clay exposed to various conditions is relevant because certain microorganisms (e.g., those that produce corrosive sulfide or gaseous metabolites) could lead to deterioration of engineered barrier components of the repository. In previous research, a high degree of variability in the abundance of culturable microorganisms among replicate samples has been observed. The purpose of this study was to test whether experimental technique (e.g., inadequate mixing of bentonite) or extremely low biomass represent mechanisms to explain such variability. Using a combination of cultivation- and DNA-based techniques to study six replicate hydrated bentonite microcosms, as well as six replicate bentonite aliquots originating from the same hydrated bentonite microcosm, the results of this study demonstrate that observed heterogeneity is likely not due to inadequate bentonite mixing. Instead, the data indicate that low biomass of as-received bentonite leads to unique microbial populations of culturable bacteria associating with each sample, or to a lesser degree within different areas of a single bentonite sample used to establish a microcosm. Because some microorganisms that grow in bentonite are culturable under commonly used cultivation conditions and others are not, this can lead to differences in culture-based abundance estimates among replicate samples. Although cultivation is a useful technique to demonstrate viability of microorganisms in bentonite, the results of this study highlight the importance of a multifaceted experimental approach (i.e., coupling cultivation to DNA-based analysis) and careful analysis of replicates when working with such low biomass samples.

The scientific and technological change at the recent speed and scale, and the vast amount of information available at everyone's fingertips, can be overwhelming. Thus, scientists and educators need to support everyone in becoming and being able to judge scientific expertise and the credibility of a source and the information provided; and need to facilitate developing or strengthening trust in science. Papers from around the globe, addressing current educational approaches that drive the development of science literacy, were published in the FEMS Microbiology Letters virtual Thematic Issue 'Learning together for our future'' in October 2025. The paper's themes of timely education practice range from public engagement with microbiology, active and authentic learning that prepares for professional and civic contributions, to citizen science and service learning. Its content is reviewed and contextualized here to facilitate discussions within the professional community. Crucially, we need to offer and create inclusive opportunities for learning and developing science literacy, so we can truly learn together for our future.

This study optimizes sustainable ectoine production in reduced salinity and minimal media to meet demands in pharmaceuticals, food, and cosmetics, isolating a halophilic bacterium 99.1% similarity to Halomonas smyrnensis from Sambhar Salt Lake. Optimization of ectoine production was performed using the one-variable-at-a-time method and Response Surface Methodology, assessing variables such as carbon and nitrogen sources, incubation time, pH, temperature, inoculum density, agitation rate, and salinity. High-Performance Liquid Chromatography confirmed total ectoine production, which increased from 0.42 g/L to 6.5 g/L, a 16.25-fold enhancement compared to initial unoptimized conditions. The optimal ectoine yield by Halomonas smyrnensis IIIM VA-6 was achieved after 72 hours under conditions of 5% (w/v) salinity, 10.0 g/L monosodium glutamate, pH 5.0, 10.0 g/L lactose, and 250 r.p.m. agitation, and characterized by FTIR, NMR, LC-MS. This study represents a significant improvement in sustainable production of ectoine under reduced salinity conditions using a halophilic strain.

Infections with epidemic PCR ribotype (RT) 027 strains are characterized by higher mortality and morbidity and have caused outbreaks in North America and Europe. To date, RT027 isolates have not conclusively been shown in Brazil, although other clade 2 isolates have been identified. This case report discusses a 60-year-old patient, with medical history of colon adenocarcinoma, who developed a severe CDI after chemotherapy, but showed a full recovery. The infection was caused by a C. difficile RT027 strain, demonstrating conclusively for the first time that this ribotype is present in Brazil. This case emphasizes the need for early CDI diagnosis of C. difficile in Brazilian hospitals for prompt treatment and notification.

Neisseria meningitidis (Nm), a commensal that colonizes the nasopharynx of 4.5%-24% of healthy humans, can cause invasive meningococcal disease (IMD). We hypothesized that distinct genotypic and/or phenotypic signatures might be found in carriage vs. invasive isolates. Carriage isolates were cultured from nasopharyngeal swabs (n = 267) collected from healthy students (aged 13-21 years) during the 2013 and 2014 school years in the Netherlands. Invasive isolates (n = 214) were cultured from all reported disease cases in the Netherlands from 2012 to 2014. Whole core genome sequences were determined for all isolates and comparisons of selected genotypic markers and phylogenomic associations between carriage and disease isolates were analyzed. While 30% of carriage isolates could not be assigned a genogroup, all the invasive isolates were successfully genogrouped. Genogroup B (MenB) predominated, representing 27% of carriage and 75% of IMD isolates. Sequence type (ST) complex diversity was dominated by four STs (ST-41/44, ST-213, ST-32, and ST-269) in both carriage and disease isolates. FHbp subfamily A variants were prevalent (79%) in carriage, whereas subfamily B variants were more frequent (69.6%) in disease. Carriage and IMD-causing Nm strains display similar ST and phylogenomic profiles; however, an increased FHbp subfamily B prevalence and an enhanced level of FHbp surface expression were noted in MenB disease-causing isolates.

Bradyrhizobium, the largest rhizobial genus, is characterized by a variety of exopolysaccharide (EPS) components, such as penta- and tetrasaccharides, depending on the species. However, several genes involved in EPS synthesis remain unknown. In this study, we investigated whether 186 Bradyrhizobium strains possess homologous genes in the EPS cluster I, which is responsible for the synthesis of a pentasaccharide EPS by B. diazoefficiens USDA110. The absence of homologous genes in the B. elkanii and Photosynthetic Bradyrhizobium supergroups, in contrast to the B. japonicum supergroup, suggests that these lineages may utilize distinct and uncharacterized genes involved in tetrasaccharide EPS biosynthesis.

Methanogens rely on compatible solutes to withstand osmotic stress, yet their responses to high ammonium concentrations, common in biogas digesters, remain poorly understood. In this study, intracellular osmolyte accumulation was examined in four Methanoculleus bourgensis strains (MAB1, MAB2, MAB3, and BA1), isolated from high-ammonia biogas digesters, under progressive increase in concentrations of ammonium and sodium chloride. Their responses were compared with those of the type strain Methanoculleus bourgensis MS2T and the halophilic Methanoculleus submarinus Nankai-1T. All investigated strain grew to 12 g l-1 NH4+-N (0.3 mg l-1 NH3), and gradual adaptation increased ammonium/ammonia tolerance in some strains to 25 g l-1 NH4+-N. Whereas the reference strains accumulated glycine betaine under both ammonium and sodium chloride stress, the M. bourgensis strains from high ammonia biogas systems uniquely accumulated Nε-acetyl-β-lysine during increasing levels of ammonium chloride. This β-amino acid derivative is known as a NaCl-induced osmoprotectant in methanogens, but it´s association with high ammonium/ammonia levels in pure cultures has not previously been demonstrated. Our findings identify Nε-acetyl-β-lysine biosynthesis as a potential mechanism underpinning the exceptional ammonium/ammonia tolerance of M. bourgensis, a taxon frequently dominating methane production in high-ammonia biogas systems, while also revealing notable variation in this trait among its subspecies.

Trichoderma fungi are colonizers of plant substrates and rhizosphere and are valued for their antagonism against phytopathogens and ability to promote plant health. We investigated Trichoderma diversity in coffee-growing soils in Caranavi region of Yungas-La Paz, Bolivia, where high humidity and fungal diseases threaten yield, and evaluated their potential as biocontrol agents against coffee pathogens. A total of 440 Trichoderma were isolated from coffee rhizosphere, fallow lands, and forest ecosystems across an altitudinal gradient in Caranavi. DNA barcode analyses using ITS, rpb2, and tef1 loci identified only four species. However, 47 taxa comprising 344 isolates were ambiguous, and 41 isolates were previously unrecognised species. The diversity of Trichoderma spp. was significantly affected by ecosystem type and altitude, with more species isolated from coffee rhizosphere than fallow lands and forest ecosystems, and from lower altitudes than higher ones. Evaluation of 100 isolates against a native coffee wilt pathogen Fusarium oxysporum identified 70 potent antagonists, with 30 achieving 90-100% disease control. This is the first comprehensive study of Trichoderma diversity in Yungas, identifying indigenous Trichoderma for biocontrol applications against coffee diseases. It also emphasizes the need to refine the Trichoderma species concept and improve the taxonomic resolution within the genus.

Plasmids of the incompatibility group H (IncH) are large mobile elements that confer multidrug resistance and are prevalent in Enterobacterales from clinical and environmental sources. We analyzed 1308 globally distributed IncH plasmid sequences to assess their genomic features and functional potential. IncH plasmids were classified into IncHI1 and IncHI2, with IncHI1 subdivided into IncHI1B and IncHI1AB based on co-occurring replication proteins. These subtypes exhibited distinct host preferences and genomic patterns. IncH plasmids carried antimicrobial resistance genes and other adaptive determinants at comparable frequencies across environments. They encoded multiple replication and relaxase proteins, supporting broad host range and plasmid exclusion. Core genes included the Hha regulator, involved in virulence and conjugation; a DNA (cytosine-5)-methyltransferase contributing to AT-rich content; Cobamide synthase, potentially linked to metal tolerance; and the ter operon, associated with tellurium resistance and stress adaptation. Integron-associated genes such as qacEΔ1, sul1, and blaIMP promoted resistance to quaternary ammonium compounds, sulfonamides, and carbapenems. Notably, ~60% of nonredundant IncH plasmids encoded sulfonamide, quaternary ammonium compound, and β-lactam resistance, while over 70% harbored aminoglycoside resistance genes. These findings highlight IncH plasmids as reservoirs of clinically relevant genes and stress-response functions, reinforcing their importance for monitoring antibiotic resistance dissemination and environmental adaptability within Enterobacterales.

Honeybees (Apis mellifera) are essential pollinators that sustain biodiversity and global food security but are increasingly threatened by bacterial infections and antimicrobial resistance (AMR). This study investigated the bacterial composition and resistance profiles of beehives from three floral micro-regions of Misurata city, Libya: Spring Flower, Thyme, and Sidr. A total of 120 isolates (40 per area) were identified using biochemical assays and tested for susceptibility to tetracycline, erythromycin, ampicillin, and chloramphenicol. Bacillus species predominated (56.7%), followed by Staphylococcus (28.3%), with minor occurrences of Pseudomonas, Enterococcus, Klebsiella, and Acinetobacter. Marked interspecific differences were detected for tetracycline, erythromycin, and ampicillin, while no chloramphenicol resistance occurred (0/120; 0%, 95% CI upper bound ≈ 3.1%). Staphylococcus aureus and Enterococcus spp. exhibited the highest resistance, contrasting with the largely susceptible Bacillus isolates, except for ampicillin resistance in B. cereus (34/40; 85.0%) and B. subtilis (6/28; 21.4%). Less frequent species tended to display stronger resistance, whereas no significant differences were observed among the three sampling areas. These findings establish the first baseline of bacterial diversity and AMR in Libyan beehives, emphasizing the need for responsible antibiotic use and continuous monitoring within apicultural ecosystems.