Fems Microbiology Letters最新文献

Chicken is the most widely consumed meat in Malaysia as it is abundant, provides good nutrient and taste, and available at an affordable price. However, it is known to harbour various foodborne pathogens including faecal microorganism, Escherichia coli. There are various routes and factors that can cause contamination of E. coli in chicken. Furthermore, numerous reports have shown that over the past decades, the trends of antimicrobial resistance among foodborne pathogens have been increasing rapidly. Therefore, the present work aimed to assess the prevalence of E. coli contamination by examining various contributing factors and its antibiotic resistance in raw chicken meat sold in Klang Valley, Malaysia. Results showed that 74% of the samples were contaminated with E. coli with wet markets showing higher prevalence (17%) of E. coli than in hypermarkets. Univariate analysis within the same risk factor showed that packaging process, storage temperature, and antibiotics had significant effects on the prevalence of E. coli (∼ 6.097 log CFU/g). The E. coli loads were significantly influenced by market type and storage temperature as validated by Mann-Whitney tests. All E. coli isolates displayed multiple antibiotic resistance (MAR) index ranging from 0.33-1.00, and 35 E. coli isolates showed the highest MAR index (1.00), being resistant to 12 antibiotics. Furthermore, 90% of E. coli isolates contained extended-spectrum beta-lactamase (ESBL) genotypes that can subvert potent antibiotic, beta-lactam. The findings from the present work would help reduce the risk of foodborne illnesses by identifying the risk factors associated with E. coli prevalence in chicken and provide the basis to revise guidelines on antibiotic use in livestock to reduce antimicrobial resistance.

Disrupting quorum sensing (QS) pathways in animal and plant pathogenic bacteria is an effective strategy to mitigate infections without promoting antibiotic and pesticide resistance. This approach inhibits the production of virulence factors, biofilm formation, and toxin production, reducing bacterial pathogenicity. In plant health protection, Bacillus spp. are extensively researched and utilized as biocontrol agents; however, the potential of their AHL-lactonase-producing ability, which plays a key role as a QS inhibitor of Gram-negative pathogens, remains largely unexplored. This study examined the activity and diversity of QQ enzymes from Bacillus spp. isolates obtained from various natural sources, confirming their presence in previously unreported environments associated with agricultural fields (straw and manure). Our findings show that AiiA lactonase is the most dominant and highly conserved AHL-lactonase among Bacillus isolates from bulk soil, manure, and straw. Despite its sequence conservation, we observed significant variation in AiiA lactonase activities towards the C6-HSL substrate. Furthermore, in silico analysis suggested that the Bacillus sp. YtnP lactonase may have a lower affinity for C6-HSL compared to AiiA lactonase. Finally, this research presents a selection of Bacillus isolates with high AiiA lactonase activity for potential testing against plant pathogens.

Three epilithic cyanobacterial strains were isolated from the scrapings of a single rock surface from the Reshi river in Sikkim, India. At the time of sampling, the rock surface did not show any visible cyanobacterial growth however the surface of the rock was glistering. Subsequent morphological analysis indicated two out of three strains exhibited typical Nostoc-like morphology and the third strain had cell division in multiple planes showing typical morphology of a member of the family Hapalosiphonaceae. Further, 16S rRNA gene phylogeny indicated the strains to be members of the genus Nostoc, Desmonostoc, and Westiellopsis. For species-level demarcation, additionally, 16S-23S ITS region analysis was performed which indicated that the strain RESHI-1B-PS was a novel cyanobacterial lineage of the genus Nostoc while the strains RESHI-1A-PS and RESHI-1C-PS were representatives of Desmonostoc sp. and Westiellopsis prolifica respectively. Thus, in the current investigation, we have described an undocumented species of the cyanobacteria, which we named Nostoc sikkimense in accordance with the guidelines outlined in the International Code of Nomenclature for algae, fungi, and plants (ICN). The study also enumerates and illustrates different life cycle stages of Nostoc sikkimense RESHI-1B-PS along with further expanding the geographic distribution of Westiellopsis prolifica and its substantial ecological adaptability.

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 Caldibacillus 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 50-60°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 (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). 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.

Antibiotic resistance and the persistence of sessile cells within biofilms complicate the eradication of biofilm-related infections using conventional antibiotics. This highlights the necessity for alternate therapy methods. The objective of this study was to investigate the biofilm destruction activity of α-tocopherol against Staphylococcus aureus, Proteus mirabilis and Pseudomonas aeruginosa on polystyrene. α-Tocopherol showed significant biofilm destruction activity on the pre-formed biofilms of S. aureus (45-46%), Pr. mirabilis (42-54%) and Ps. aeruginosa (28%). Resazurin assay showed that α-tocopherol disrupted all bacteria biofilms without interfering with their cell viability. Scanning electron microscope images showed lower bacterial cell count and less compacted cell aggregates on polystyrene surfaces after treatment with alpha-tocopherol. This study demonstrated the biofilm destruction activity of alpha-tocopherol against S. aureus, Pr. mirabilis and Ps. aeruginosa. α-Tocopherol could potentially be used to decrease biofilm-associated infections of these bacteria.

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.

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.

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.

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.