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.

Efficient screening methods are crucial for developing phage cocktails that can sustainably suppress bacterial growth. We developed a regrowth culture-guided phage screening strategy using Salmonella Enteritidis as a model. The strategy comprises four steps: (1) isolating an initial phage through conventional random screening, (2) generating a regrowth culture from bacteria that survive phage-induced inhibition, (3) enriching a phage pool by coincubating the regrowth culture with environmental samples, and (4) isolating phages that infect the regrowth-adapted bacterial population. Compared to cocktails derived from conventional random or mutant-based screening approaches, those prepared via this strategy demonstrated prolonged inhibitory activity, effectively suppressing S. Enteritidis regrowth for over 24 h in liquid culture. This approach provides a simple, reproducible, and ecologically relevant method for identifying phages with enhanced efficacy against phage-evasive bacterial populations. It may also serve as a valuable screening framework for developing robust phage cocktails against other pathogens.

Two bacterial strains degrading liquefied polypropylene (PP) at a moderately high temperature of 50°C were obtained after enrichment on liquefied PP in surface seawater supplemented with nitrogen, phosphorus, and iron nutrients at 50°C. The strains, designated R1 and R4-2, belonged to Nitratireductor and Oricola, respectively. These genera are phylogenetically close. Nitratireductor R1 or its close relatives were detected as the main bacteria (12% of the total bacteria) and Oricola R4-2 or its close relatives were also significantly detected (5%) in the liquefied PP-enriched seawater, suggesting that these bacteria utilized liquefied PP as a carbon source. Nitratireductor R1 showed liquefied PP-degrading activity at 50°C but not at 28-42°C, while Oricola R4-2 showed the activity at 42-50°C but not at 28°C. At 50°C, these two strains degraded liquefied PP of all lengths detected, isoprenoid-derived branched alkane (pristane), and n-alkane (n-hexadecane) to a similar extent, and also degraded aromatic compounds. Pristane and n-hexadecane appeared not to induce the PP-degrading activity. These results indicate that Nitratireductor and Oricola bacteria could be used in industrial applications for degrading liquefied PP and polyethylene and aromatic structures of liquefied aromatic-containing plastics at 50°C.

Fenclorim is an effective safener that protects rice (Oryza sativa L.) from the phytotoxic effects of certain herbicides. This study investigated its impact on soil bacterial communities, isolated fenclorim-degrading bacteria, assessed environmental contamination by fenclorim and other pesticides, and enhanced their degradation in soil and water under aerobic conditions. Results showed that fenclorim did not adversely affect the bacterial community structure. Acinetobacter sp. F0, capable of using fenclorim as a sole carbon, nitrogen, and energy source, was isolated from soil and degraded 97.1 ± 1.2% of fenclorim (100 µM) within 36 h. Fenclorim was more persistent in soil and water than pretilachlor, butachlor, and pymetrozine. Co-inoculation with target-degrading microorganisms significantly enhanced the degradation of all compounds and reduced the accumulation of intermediate metabolites-4,6-dichloropyrimidine and benzene-via cross-degradation. A packed-bed bioreactor achieved degradation efficiencies of 93.7 ± 4.59% for fenclorim, 94.9 ± 4.09% for pretilachlor, and 90.4 ± 5.52% for butachlor at a 12-h hydraulic retention time. The reactor also effectively removed BOD5, COD, NO3-, NH4+, and PO43- from water. These findings provide valuable insights into fenclorim degradation pathways, pesticide persistence, and the role of microbial augmentation in environmental remediation.

Crystal-violet staining, microscopy with image analysis, and quantitative PCR (qPCR) were compared to examine biofilm dynamics. Biofilms of 30 polycultures comprising 15 bacterial species were monitored for 14 days. Collectively, qPCR (representing population) revealed a different growth pattern compared to staining (biomass) and microscopy (colonization): biomass and colonization gradually increased over time, whereas population increased rapidly for the first seven days and leveled off. Temporal forms were categorized into two growth patterns: continuous increase (CI) and non-continuous increase. Staining and microscopy showed similar odds of detecting the CI pattern (27 and 23 polycultures, respectively) across polycultures, greater than that of qPCR (14 polycultures) (P < 0.05). All three methods revealed the identical patterns for 13 polycultures. Staining with microscopy, staining with qPCR, and microscopy with qPCR found the same patterns in 22, 15, and 19 polycultures, respectively. Additionally, staining was quantitatively agreed with microscopy (P < 0.05; R2 > 0.50), whereas neither staining nor microscopy strongly agreed with qPCR (P < 0.05; R2 ≤ 0.22). Collectively, staining was more compatible with microscopy than qPCR in characterizing biofilm dynamics and quantifying biofilms owing to the difference between population growth and biofilm expansion. The concurrent use of qPCR with biomass estimations allows for accurate and comprehensive biofilm quantification.

SARS-CoV-2 infection is an acute respiratory distress syndrome associated with immune dysfunction, causing coronavirus disease 2019 (COVID-19) disease. The use of immunosuppressive drugs in its treatment increases the risk of opportunistic infections. In particular, opportunistic fungal infections have been described in initially non-immunocompromised patients with severe COVID-19 disease. Among them, rare cases of cryptococcosis have been described. Here we present the first two French cases of non-HIV non-transplant patients who developed disseminated Cryptococcus neoformans fungal infection in the setting of severe COVID-19 disease. Blood cultures appear to be an interesting diagnostic tool for post-COVID-19 cryptococcosis, which is an often fatal complication.