Fems Microbiology Letters最新文献

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.

Commensal Neisseria are members of a healthy human oropharyngeal microbiome; however, they also serve as a reservoir of antimicrobial resistance for their pathogenic relatives. Despite their known importance as sources of novel genetic variation for pathogens, we still do not understand the full suite of resistance mutations commensal species can harbor. Here, we use in vitro selection to assess the mutations that emerge in response to ciprofloxacin selection in commensal Neisseria by passaging four replicates of four different species in the presence of a selective antibiotic gradient for 20 days; then categorized derived mutations with whole genome sequencing. Ten out of sixteen selected cells lines across the four species evolved ciprofloxacin resistance (≥1 ug/ml); with resistance-contributing mutations primarily emerging in DNA gyrase subunit A and B (gyrA and gyrB), topoisomerase IV subunits C and E (parC and parE), and the multiple transferable efflux pump repressor (mtrR). Of note, these derived mutations appeared in the same loci responsible for ciprofloxacin-reduced susceptibility in the pathogenic Neisseria, suggesting conserved mechanisms of resistance across the genus. Additionally, we tested for zoliflodacin cross-resistance in evolved strain lines and found 6 lineages with elevated zoliflodacin minimum inhibitory concentrations. Finally, to interrogate the likelihood of experimentally derived mutations emerging and contributing to resistance in natural Neisseria, we used a population-based approach and identified GyrA 91I as a substitution circulating within commensal Neisseria populations and ParC 85C in a single gonococcal isolate. A small cluster of gonococcal isolates shared commensal alleles at parE, suggesting recent cross-species recombination events.

Terminal olefins are important platform chemicals, drop-in compatible hydrocarbons and also play an important role as biocontrol agents of plant pathogens. Currently, 1-alkenes are derived from petroleum, although microbial biosynthetic routes are known. Jeotgalicoccus sp. ATCC 8456 produces 1-alkenes via the fatty acid decarboxylase OleTJE. UndA and UndB are recently identified non-heme iron oxidases converting medium-chain fatty acids into terminal alkenes. Our knowledge about the diversity and natural function of OleTJE, UndA, and UndB homologs is scarce. We applied a combined screening strategy-solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME GC-MS) and polymerase chain reaction (PCR)-based amplification-to survey an environmental strain collection for microbial 1-alkene producers and their corresponding enzymes. Our results reinforce the high level of conservation of UndA and UndB genes across the genus Pseudomonas. In vivo production of defined 1-alkenes (C9-C13; C15; C19) was directed by targeted feeding of fatty acids. Lauric acid feeding enabled 1-undecene production to a concentration of 3.05 mg l-1 in Jeotgalicoccus sp. ATCC 8456 and enhanced its production by 105% in Pseudomonas putida 1T1 (1.10 mg l-1). Besides, whole genome sequencing of Jeotgalicoccus sp. ATCC 8456 enabled reconstruction of the 1-alkene biosynthetic pathway. These results advance our understanding of microbial 1-alkene synthesis and the underlying genetic basis.

This study assesses halophilic archaea's phylogenetic diversity in southern Tunisia's geothermal water. In the arid southern regions, limited surface freshwater resources make geothermal waters a vital source for oases and greenhouse irrigation. Three samples, including water, sediment, and halite soil crust, were collected downstream of two geothermal springs of the Ksar Ghilane (KGH) and Zaouet Al Aness (ZAN) oases, Tunisia. The samples were subjected to 16S rRNA gene sequencing using the Illumina Miseq sequencing approach. Several haloarchaea were identified in the geothermal springs. The average taxonomic composition revealed that 20 out of 33 genera were shared between the two geothermal sources, with uneven distribution, where the Halogranum genus was the most represented genus with an abundance of 18.9% and 11.58% for ZAW and KGH, respectively. Several unique site-specific genera were observed: Halonotius, Halopelagius, Natronorubrum, and Haloarcula in ZAN, and Haloprofundus, Halomarina, Halovivax, Haloplanus, Natrinema, Halobium, Natronoarchaeum, and Haloterrigena in the KGH pool. Most genus members are typically found in low-salinity ecosystems. These findings suggest that haloarchaea can disperse downstream from geothermal sources and may survive temperature and chemical fluctuations in the runoff.

Bacteria that ferment amino acids to ammonia can be categorized as generalists or specialist hyper-ammonia-producing bacteria. In the rumens of ruminant animals, most of the ammonia produced is eventually excreted as urea in urine. This process can be controlled with off-label use of antibiotics, but the practice can lead to antibiotic resistance; therefore, discovery of antibiotic alternatives is pertinent. Plant-derived phenolic compounds have demonstrated antimicrobial efficacy for such purposes. This study investigated the antimicrobial and metabolic suppressive potential of six phenolic compounds on five amino acid fermenting bacteria: Clostridium sporogenes MD1, C. aminophilum F, Acetoanaerobium sticklandii SR, Peptostreptococcus sp. BG1, and Prevotella bryantii B14. Inhibitory action of the compounds was determined using a 10% v/v serial dilution method in basal media. Carvacrol (1 mM), thymol (1 mM), and eugenol (10 mM) demonstrated the greatest antimicrobial potential, where carvacrol and eugenol inhibited growth of all five species and thymol four species except BG1. The cinnamic acids (trans and hydro) demonstrated variable activity against all organisms. Suppression of metabolic activity was determined via colorimetric assay quantifying ammonia in washed stationary phase culture supernatant after 24 h of metabolism on fresh substrate. Carvacrol and eugenol yielded the greatest reduction of ammonia by all organisms except B14, which produced no ammonia under the growth conditions. Thymol greatly reduced ammonia production of four organisms except F. These data demonstrate that eugenol, carvacrol, and thymol may be worthy antimicrobial candidates for the control of ammonia-producing organisms.

Scientific conferences are essential to academic exchange. However, related air travel contributes to greenhouse gas emissions, while expensive registration and travel costs limit the participation of early career researchers and those from low-income countries. Virtual conferences offer promising solutions for reducing emissions and enhancing accessibility and inclusivity but often limit networking and personal interaction. Hybrid multi-hub conferences, which combine virtually connected in-person venues with individual virtual participation, combine the benefits of both conference formats. Thus, we present and discuss MEEhubs2024, a multi-hub conference on microbial ecology and evolution held in January 2024. During this 3-day conference, attendees participated virtually or at one of six hubs in Europe and North America. We analyzed the participants' and organizers' feedback to create a template and provide insights into the scientific community's adoption of this new conference format, which was positively evaluated by most participants. Because technical, logistical, and structural challenges remain, including limited opportunities to interact and network across hubs and participation modes, we provide recommendations for improvement, such as hiring technical hosts and offering virtual-only social activities. Finally, we used the participants' feedback to reflect on conference expectations, highlighting research gaps and the need for organizers to define and communicate goals when organizing conferences.