Fems Microbiology Letters最新文献

Infections with epidemic polymerase chain reaction 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 Clostridioides difficile infection (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 RT is present in Brazil. This case emphasizes the need for early CDI diagnosis of C. difficile in Brazilian hospitals for prompt treatment and notification.

SMC (Structural Maintenance of Chromosomes) ATPase proteins are integral components of complexes bearing the same name, crucial for the spatial organization of DNA across diverse life forms, spanning bacteria, archaea, and eukaryotes. It is proposed that in bacteria, SMC complexes facilitate DNA compaction through loop extrusion and aid in the segregation of daughter nucleoids. In this paper, the properties of the SMC ATPase protein from Ureaplasma parvum were investigated by using a spectrum of methods, including conventional biochemical methods as well as advanced single-molecule techniques. Our findings reveal distinctive properties of this protein compared to its extensively studied homologue from Bacillus subtilis. Notably, our results suggest that U. parvum Smc ATPase facilitates DNA compaction even in the absence of ATP.

Aeration is a common pretreatment method to enhance biogas production via anaerobic digestion of waste organic feedstocks such as unused food. While impacts on downstream anaerobic digestion have been intensively investigated, the consequence of aeration on the microbial community in food waste has not been characterized. Food waste has a low pH resulting from the dominance of lactic acid bacteria within the Firmicutes phylum. This excludes other phylotypes with a higher potential to hydrolyse complex biopolymers in food waste. In this study, we reveal that aeration of macerated food waste results in a dramatic shift away from Firmicutes towards dominance of Proteobacteria that are better known for extracellular enzyme production. Given that hydrolysis is the rate limiting step in anaerobic digestion, this explains why aeration improves the efficiency of biogas production from food waste. The discovery that Proteobacteria dominate microbial communities in aerated food waste opens up opportunities to manipulate extracellular enzyme production through gene expression mechanisms common among Proteobacteria such as quorum sensing.

Gut microbes form a complex and dynamic symbiotic relationship with their host. However, the microbial response during the early stages following host death remains largely uncharacterized. In this study, we employed a mouse model to systematically characterize the postmortem response of the intestinal microbiota, and analyzed the dynamic changes in microbial composition during the early stages after death in both male and female mice (at 0, 0.5, 2, 6, 12, and 24 h postmortem). Our findings reveal that sex-dimorphic shifts in microbiome composition occur as early as 2 h postmortem. Male mice exhibited increased functional redundancy and delayed community restructuring, whereas female mice displayed earlier community shifts. These sex-specific patterns were accompanied by differences in metabolic pathway activity and biomarker taxa. Notably, the observed retention of regulatory capacity by intestinal microbes after host death offers a novel perspective on the conceptualization of death itself. We propose the term "ecological death" to describe the irreversible collapse of the host-associated microbial ecosystem following death, marking a critical transition in the functional and structural integrity of the intestinal microbiota.

The present study analysed the sensory quality and fungal community structure of three color types of high-temperature Daqu (HTD) produced in Qingzhou using electronic nose, electronic tongue, and high-throughput sequencing technology. The data were compared to the fungal data obtained from HTD produced in Xiangyang via the "partitioning around medoids" (PAM) clustering algorithm. PAM analysis indicated that all HTD samples from the two regions could be divided into two clusters. Cluster I samples were mainly characterized by Thermomyces, and cluster II samples were mainly characterized by Aspergillus and Thermoascus. Cooccurrence network analysis revealed that the correlations between fungal communities were stronger in the HTD dominated by Aspergillus and Thermoascus. The identification of key species and core operational taxonomic units demonstrated that the differences in the fungal community structure between the two HTD clusters were related to the abundance of certain fungal groups. Correlation analysis between fungal genera and sensory quality parameters showed that Thermomyces-dominated HTD had lower aftertaste-A, aftertaste-B, and organic sulfide and terpene content but a higher richness of flavor. Meanwhile, HTD dominated by Aspergillus and Thermoascus exhibited the opposite traits, and its sourness was relatively higher.

Host-associated microbiomes have significant impacts on host biology and physiology, but the underlying processes governing their structure and assembly are not well understood. One approach to better understanding those process is the use of computationally driven modeling tools, such as network analysis to identify patterns of cooccurring taxa across microbiomes. Those patterns can then be tested to identify taxa that are potentially more important in the overall structuring and assembly processes. Here, we used network analysis to explore cooccurrence patterns within the microbiome of Aedes albopictus. We identified important nodes in the network using the centrality metrics of node degree and betweenness. Among the nodes with the highest centrality values, more ITS ASVs were present than 16S ASVs. We then tested the network analysis predictions in vivo/in situ in A. albopictus. A series of exclusion experiments were used to manipulate environmental microbiome source pools by filtering the source pool by cell size. Our results show that including microbial eukaryotes, such as fungi, in the source pool affects microbiome assembly and structure in A. albopictus, which aligns with the network analyses predictions of this system. To our knowledge, this is the first study to integrate microbial network centrality analysis with in vivo/in situ validation using filtration-based microbial community exclusion.

The preparation of silver nanoparticles (AgNPs) via an environmentally friendly green synthesis method represents an ecologically promising alternative. This research aims to develop sustainable and eco-friendly AgNPs using the lignin peroxidase (LiP) enzyme from Caldibacillus thermoamylovorans, cultivated on waste walnut shells, which are rich in lignin, to meet the growing demand for AgNPs. Among thermophilic bacteria that were isolated, the C. thermoamylovorans SA1 strain showed the highest LiP activity. The production of LiP was optimized by adding waste walnut shells and manipulating the environmental parameters. The optimal conditions were determined at 50 g/l shell amount, 96 h, pH 8, 140 rpm, and 60°C. In parallel with the increase in enzyme activity, bacterial growth also increased. As a result of the optimization, the highest enzyme activity value was 435.0 U/ml and bacterial growth was determined to be OD600: 2.09. The extracellular medium obtained from the bacteria grown in walnut shell medium was then added to an AgNO3 solution. Efficient production of AgNPs was achieved by stirring the mixture at 50°C-60°C for 4 h under optimum conditions. The synthesized AgNPs were characterized using a range of analytical techniques, including UV‒Vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The biological efficacy of the synthesized AgNPs was evaluated by assessing their antibacterial activity against pathogenic bacteria, such as Escherichia coli O157:H7, Klebsiella pneumoniae, Staphylococcus aureus, Streptococcus pyogenes, and Bacillus cereus. The highest activity was observed against B. cereus (15 mm). The broad-spectrum antibacterial properties exhibited by the AgNPs synthesized in this study offer a promising and sustainable solution for diverse applications in various sectors, including the environmental, agricultural, medical, and pharmaceutical fields.

Chlorhexidine, an antimicrobial with a broad inhibitory spectrum, is commonly used to treat oral infections as an active ingredient in mouthwash. While typically used at high concentrations (1-2 mg/ml), oral bacteria can be exposed to sublethal concentrations due to the bioavailability and protective barrier of biofilms (dental plaques). Sublethal concentrations can cause transcriptional remodelling of bacteria such as Streptococcus mutans, a key player in dental caries. Using an RNA-seq approach, this report provides a compendium on the effect of sublethal concentrations of chlorhexidine on the transcriptome of S. mutans as planktonic cells and in biofilm states. Streptococcus mutans showed major transcriptional remodelling between planktonic and biofilm states. The transcriptional response towards chlorhexidine was more pronounced in planktonic cells compared to sessile cells. However, the response observed for biofilm-associated cells was not specific to chlorhexidine, as the transcriptional response in biofilms exposed to the β-lactam amoxicillin was similar to those observed for chlorhexidine. Furthermore, we found that S. mutans modulates the transcription of a multitude of ABC transporters in both planktonic and biofilm-associated cells upon exposure to these antimicrobials.

Enterohemorrhagic Escherichia coli O157:H7 (E. coli O157) strains do not produce curli and do not form biofilms, but they retain their ability for autoaggregation. In our study, we investigated whether curli expression would impact E. coli O157 autoaggregation. Curli-expressing strain CPM1 was derived from E. coli O157 strain ATCC 43890 as a clone forming red colonies on Congo red (CR)-agar. To quantitatively evaluate autoaggregation we applied a recently developed experimental system based on magnetic levitation. The efficiency of autoaggregation was evaluated by the geometry of macroautoaggregates and by relative amounts of aggregated and free-swimming bacteria. The curli producing CPM1 strain's autoaggregates had a volume 3.4 times smaller than that of ATCC 43890, despite the number of autoaggregated CPM1 bacteria being higher. Curli proteins were incorporated into matrix, making CPM1 autoaggregate more compact. Curliated CPM1 bacteria adhered better to vertical surfaces reducing the number of free swimmers. The Ser206Phe substitution in the transcriptional regulator RcsB was responsible for CPM1 curli-expressing phenotype. The mutation affected RcsB interactions with the accessory protein RscA. RcsA hyperexpression inhibited curli production and decreased efficiency of autoaggregation. Taken together, the obtained results demonstrated that removal of RcsB/RcsA-dependent inhibition of curli expression improves autoaggregation in the E. coli O157.

A practical storytelling approach can help scientists transform their complex research into engaging narratives. This commentary discusses a practical workshop setup through which scientists can focus on leveraging emotions, character development, logical connections and active language to enhance science communication with both expert and nonexpert audiences.