Fems Microbiology Letters最新文献

NAI-107 has demonstrated in vitro and in vivo efficacy against multidrug-resistance (MDR) pathogens. Studies using the Galleria mellonella model found NAI-107 effective against Neisseria gonorrhoeae and vanB-resistant Enterococcus faecium, with no toxicity at concentrations up to 64 µg/ml. This pilot study evaluated NAI-107's safety using transgenic zebrafish embryos (kdrl:eGFP) that were exposed to NAI-107 concentrations of 0, 10, 20, and 30 µM from 5 hours post-fertilization (hpf) to 4 days post-fertilization (dpf). No mortality or significant morphological abnormalities were observed across all treatment groups. At 2 dpf, larvae treated with 20 and 30 µM NAI-107 exhibited a significant increase in heart rate (P < 0.05), although other cardiac parameters remain unaffected. At 4 dpf, larvae displayed no significant growth differences but had increased locomotor activity at 20 and 30 µM NAI-107 groups, indicated by the higher total distance moved and mean velocity (P < 0.05). NAI-107, at concentrations up to 30 µM, did not induce significant toxic effects in zebrafish embryos. The absence of adverse impacts on survival or gross morphology suggests a favorable safety margin. However, the observed increases in heart rate and locomotor activity suggest possible subclinical effects at higher concentrations that warrant further investigation.

Secreted nucleases, either cell-attached or released in the environment, play varied roles in bacteria-host interactions during an infection. They help to provide nucleotides essential for bacterial growth by degrading host nucleic acids, are involved in the degradation of extracellular traps and hence in immune evasion, and can have direct cytotoxic activity in host cells. Nuclease expression in bacteria of the Mycoplasma genus has been poorly studied so far. In this study, a standardized set of methods was used to detect the in vitro nuclease activities of major animal mycoplasmas. Nucleases were detected in swine (Mycoplasma (M.) hyopneumoniae, M. hyorhinis, and M. flocculare) as well as avian (M. gallisepticum, M. iowae, and M. synoviae) species, but not in the small ruminant subspecies M. mycoides subsp. capri and M. capricolum subsp. capricolum. In swine species, nuclease activity was detected in both the cell pellet and the supernatant, whereas in poultry species, the results were more variable. We showed that detection of nuclease activity-in terms of presence/absence in our experimental conditions-was strain dependent in M. iowae and M. synoviae. The DNA from macrophage extracellular traps was further demonstrated to be a substrate for mycoplasma-expressed nucleases, suggesting that several Mycoplasma species and/or strains infecting animals could feed on resulting nucleotides and hence escape the traps, two features contributing to persistence of the infection.

In this study designed to isolate lactic acid bacteria (LAB) with bacteriocin production potential, white cheese samples were collected from different provinces of Turkey and isolation was carried out. A series of experiments were carried out for the main purpose and the actual bacteriocin producers were identified by detecting the genes encoding this bacteriocin. The experiments carried out in this direction were initially carried out with 20 isolates and as a result of various experiments, the number of isolates was reduced to 8 and the study was continued with 8 isolates. In order to determine that the eight isolates identified as a result of a phenotypic and biochemical characterization study were true bacteriocin-producing strains, their antibacterial activity was investigated and then the presence of bacteriocin genes was examined by specific polymerase chain reaction (PCR) using gene-specific primers. As a result, MS16 coded Lactiplantibacillus plantarum OR922652 was found to have strong antibacterial activity against Escherichia coli, Klebsiella pneumonia, Yersinia enterocolitica, Listeria monocytogenes, Bacillus cereus, and Staphylococcus aureus; the isolate was susceptible to clinically important antibiotics (ciprofloxacin, gentamicin, penicillin G, ampicillin, chloramphenicol, and vancomycin) and resistant to erythromycin, had no hemolytic activity and possessed plnA and plnD genes encoding bacteriocin production. In conclusion, the MS16 coded L. plantarum isolate has emerged as a promising strain that can be used especially in the health field and in the food industry related to LAB.

Bacillus thuringiensis (Bt) is an insect pathogen that primarily relies on pore-forming toxins known as Cry proteins to kill its insect larval hosts. The effectiveness of Cry proteins has driven a worldwide search for Bt strains to identify and characterize novel insecticidal proteins with different specificities. In this study, Bt genome analysis revealed two consecutive open reading frames that are highly similar to the N-terminal of Cry14Aa1 and the C-terminal of Cry21Ca2, both of which target nematodes. The two genes can be cotranscribed as a functional operon; however, when expressed individually, neither gene forms crystalline inclusions. In contrast, operon-based co-expression restores crystal formation and confers nematicidal activity comparable to that of the full-length Cry14Aa protein. These findings demonstrate that the Bt genome encodes fragmented yet structurally complementary toxin genes that functionally reconstitute via operon-mediated co-expression. This work provides important insights into the functional recombination of Bt toxin genes and offers a novel model for the engineering of biopesticides.

Nucleocytoviruses have extraordinarily large double-stranded DNA genome, including a set of highly conserved genes for viral reproduction. Meanwhile, nucleocytoviruses supposedly acquire new genes from cellular organisms and different lineages of nucleocytovirus, leading to their evolution. Although horizontal gene transfer among nucleocytoviruses is thought to occur in cells simultaneously infected by distinct nucleocytoviruses, it remains unknown which combination of lineages can co-infect a host cell. Here, we performed co-infection experiments using cedratvirus, megavirus, mollivirus, and pandoravirus. By transmission electron microscopy, we observed Acanthamoeba castellanii cells incorporating two distinct viral species in all six combinations. Furthermore, A. castellanii cell incorporating all four viral species was observed. In these experiments, a simultaneous increase in viral particles was observed for the combination of mollivirus and pandoravirus, pandoravirus and cedratvirus, mollivirus and cedratvirus, and megavirus and cedratvirus. Furthermore, transcription levels of cedratvirus and megavirus genes in the co-infected culture were significantly lower than those in the mono-infected culture based on time-course experiments, suggesting that distinct nucleocytoviruses may compete for viral reproduction. This is the first report experimentally demonstrating that co-infection of distinct nucleocytoviruses occurs in a A. castellanii cell.

The rapid dissemination of antibiotic resistance genes (ARGs) represents a significant global threat, with wastewater treatment plants (WWTPs) playing an important role as reservoirs and propagation hubs. In this study, we performed whole-genome sequencing and bioinformatic analyses on eight multidrug-resistant Escherichia coli isolates previously obtained from domestic WWTPs in Costa Rica. We identified 61 ARGs (23 unique), with 40 located on plasmids, and 21 on chromosomal sequences, seven of which were within integrons. Several ARGs were associated with resistance to clinically and veterinary important antibiotics, including sulfamethoxazole/trimethoprim, beta-lactams, and tetracyclines. One hundred twenty-one virulence-associated genes (29 unique) were detected, with 16 located on plasmids. Notably, the presence of virulence factors such as ompT and hlyF genes alongside ARGs on plasmids underscores the transmissible pathogenic potential of WWTP-associated E. coli strains. These findings highlight the role of small domestic WWTPs in disseminating pathogenic and multidrug-resistant bacteria and their mobile genetic elements, emphasizing the need for further research to understand how these discharges impact aquatic environments.

Pseudomonas aeruginosa has increasing clinical relevance and commonly occupies the cystic fibrosis (CF) airways. Its ability to colonize and persist in diverse niches is attributed to its large accessory genome, where prophages represent a common feature and may contribute to its fitness and persistence. We focused on the CF airways niche and used 197 longitudinal isolates from 12 patients persistently infected by P. aeruginosa. We computationally predicted intact prophages for each longitudinal group and scored their long-term persistence. We then confirmed prophage inducibility and mapped their location in the host chromosome with lysate sequencing. Using comparative genomics, we evaluated prophage genomic diversity, long-term persistence, and level of genomic maintenance. Our findings support previous findings that most P. aeruginosa genomes harbour prophages some of which can self-induce, and that a common CF-treating antibiotic, ciprofloxacin, can induce prophages. Induced prophage genomes displayed high diversity and even genomic novelty. Finally, all induced prophages persisted long-term with their genomes avoiding gene loss and degradation over 4 years of host replication in the stressful CF airways niche. This and our detection of phage genes, which contribute to host competitiveness and adaptation, lends support to our hypothesis that the vast majority of prophages detected as intact and inducible in this study facilitated their host fitness and persistence.

Akanthomyces lecanii is an entomopathogenic fungus, and spores of this fungus could be incorporated into films generated using cast film extrusion for biocontrol applications. However, the extrusion process involves high temperature processing (150°C) although this only lasts for a few minutes. The elevated temperature destroys spores, thereby eliminating functionality, unless the spores are protected from this heat. Initial experiments revealed that the heat tolerance of free A. lecanii spores to be 60°C. The spores were therefore encapsulated into beads prepared using a combination of Gelrite, cellulose, and Cel-fine at different concentrations. The beads were freeze-dried and then immersed in hot glycerol for 2 min at a selected temperature within the range of 50°C-100°C. The results indicated that some combinations of encapsulating agents resulted in the spores retaining viability (plate counting) after heat treatment at 100°C. Beads stored at room temperature for 1 week showed a reduction in the upper temperature tolerance. This study revealed that the temperature tolerance of A. lecanii spores could be improved by 40°C by encapsulation in freeze-dried beads containing 2% Gelrite (purified gellum gum), 0.4% cellulose, and 0.4% Cel-fine.