FEMS microbes最新文献

Toxoplasma gondii, an obligate intracellular parasite, acquires host nutrients to sustain its intracellular replication. A key interaction involves host mitochondrial association (HMA) with the parasitophorous vacuole membrane, previously thought to be strain- and cell-type-dependent, and notably absent in type 2 strains in fibroblasts. Here, we report that in human skeletal muscle KD3 myotubes, all three archetypal T. gondii strains-including type 2-demonstrate significant HMA. This association was confirmed by mitotracker staining and transmission electron microscopy. Notably, HMA appears to correlate inversely with the parasite's uptake of exogenous ¹³C-labeled fatty acids, suggesting a competitive nutrient environment shaped by host mitochondrial proximity. These findings highlight host cell-type specificity in mitochondrial interactions and suggest that HMA may function as a modulator of nutrient acquisition in a context-dependent manner. This work revises the understanding of strain-specific HMA and underscores the complexity of host-parasite metabolic interactions in muscle tissue, a physiologically relevant niche for chronic T. gondii infection.

Klebsiella pneumoniae is a critical pathogen often associated with multidrug resistance and hypervirulence. We report the isolation and characterization of three distinct lytic bacteriophages-Spear, Loop, and Shorty-from sewage, using a hypervirulent, hypermucoid K. pneumoniae K1 ST23 strain as the host. Despite genomic and structural differences, all three phages exhibited a narrow host range, infecting only the K1 serotype. Transmission electron microscopy and genomic analyses confirmed their lytic lifestyle and classifications: Spear and Loop are siphovirus-like, while Shorty is podovirus-like. A key focus was phage-host interaction and receptor usage. DNA sequence analysis showed no homology between the receptor-binding proteins, yet structural modelling revealed high similarity between Loop and Shorty tail fibers, aligning within a K1-specific lyase domain, suggesting phage genetic mosaicism. All three phages rely on capsular polysaccharide (CPS) for infection. Resistance selection under phage pressure yielded non-mucoid mutants, characteristic of CPS loss. Cross-resistance and adsorption assays confirmed CPS-dependence. Loop and Shorty showed near-complete loss of binding; Spear retained partial binding, suggesting additional receptors. These results highlight that unrelated phages can target the same bacterial structure, CPS. This has important implications for rational phage cocktail design, as CPS mutations may undermine seemingly diverse phage combinations.

Listeria monocytogenes is a food-borne pathogen that can cause severe disease in immunocompromised persons, and its ability to survive stressors encountered in food production environments (FPEs) makes it difficult to eliminate from the food chain. Previous transcriptomic analysis revealed that in response to lactic acid exposure, L. monocytogenes significantly upregulates Rli47, a noncoding RNA that has previously been shown to interact with the ilvA transcript and suppress growth of L. monocytogenes in the absence of isoleucine. We show that at logarithmic phase, an rli47 deletion mutant had a higher survival compared to the parent strain after exposure to lactic acid. Flow cytometry indicated that lactic acid exposure did not differentially affect the proportion of metabolically active cells in the deletion mutant and wild type. Transcriptomic analysis and in silico target prediction suggested that Rli47 could affect pathways involved with cell envelope structure; due to the link between cell envelope integrity and organic acid stress, it is possible that in the absence of rli47 the cell envelope of logarithmic phase L. monocytogenes cells is more resistant to lactic acid exposure. These results suggest that Rli47 functionality may vary due to factors including temperature and nutrient availability.

Interactions between viruses and sub-inhibitory concentrations of surfactants in water systems are understudied. At concentrations below the minimum inhibitory concentration (MIC), surfactants may interact with virus surface proteins without virus inactivation and alter virus surface properties. This study determined the MIC of benzyldimethyldodecylammonium chloride (BAC) and sodium dodecyl sulfate (SDS) on human adenovirus (ADV, non-enveloped, dsDNA) and mouse hepatitis virus (MHV, enveloped, ssRNA), and how sub-MIC surfactants influence virus isoelectric point (IEP), hydrated diameter, and interact with virus surface proteins. Both surfactants had MICs of 1 mg/L over 60 minutes. Experimental IEPs were lower than IEPs estimated based on amino acid structures. The ADV IEP was 3.8 without surfactants and dropped to 3.3 with BAC and lower than 3 with SDS. The MHV IEP was 4.2 without surfactants and decreased to 4.1 with SDS and 3.4 with BAC. Dynamic light scattering showed SDS and BAC decreased ADV hydrated diameter from 142 ± 8 nm (no surfactant) to 109-116 nm, while MHV decreased from 150 ± 10 nm (no surfactants) to 132-140 nm upon surfactant exposure. Molecular dynamics simulations revealed that SDS, due to its multivalent sulfate headgroup, forms numerous intimate contacts with the MHV spike protein that markedly perturb its electrostatic environment. In contrast, BAC engages only sporadically and diffusely with the protein, indicating a much weaker influence on its structure and electrostatics. Overall, this study showed that ionic surfactants can influence virus properties thus altering virus interactions with surfaces in engineered and natural systems.

Gram-negative bacteria can use type III secretion systems to inject effector proteins into eukaryotic target cells. Most effectors are co-expressed with specific chaperone proteins that are required for the secretion of their cognate effector. Although chaperones share characteristics across species, no common mechanism of action has been identified. In particular, it remains unclear, if and how chaperones target effectors to the type III secretion injectisome. In this study, we analyzed the interaction network, cellular localization, mobility, and function of SycH and SycE, two Yersinia enterocolitica T3SS chaperones, in live bacteria. While both chaperones strongly interacted with their cognate effectors, SycH additionally bound two negative regulators, YscM1/2, whereas SycE consistently showed weak interactions and proximity to various other effectors. In contrast, the chaperones did not specifically interact with the injectisome or the cytosolic T3SS components that were recently found to shuttle effectors to the injectisome. Mobility measurements and single particle tracking support these findings. Taken together, our results indicate a handover of the effector YopH from its chaperone SycH to the shuttle complexes in the bacterial cytosol and raise the possibility that a similar mechanism applies to other effector/chaperone pairs .

Extraintestinal pathogenic Escherichia coli (ExPEC) is a major cause of urinary tract infections, bacteraemia, and sepsis. CFT073 is a prototypic, urosepsis isolate of sequence type (ST) 73. ST73 isolates are associated with higher virulence scores than other pandemic clonal groups, such as ST131. This laboratory, among others, has previously shown that strain CFT073 is serum-resistant, with virulence factors such as the exopolysaccharide capsule and other extracellular polysaccharides imparting resistance to the complement system. In this study, it was shown that culture supernatants were protective in standardized serum killing assays, when compared to cultures standardized in fresh medium. Diluting cultures in fresh medium in place of conditioned medium significantly increased sensitivity of CFT073 to serum, indicating that a secreted factor may provide resistance to serum. Haemolysin, a pore-forming toxin, is secreted by CFT073 in a calcium-dependent manner. This study found that a CFT073 hlyA mutant is significantly more sensitive to 50% serum than the wild-type, implicating haemolysin in the response of CFT073 to serum. In addition to acting as a toxin upon secretion, it has been shown previously that HlyA forms a complex with lipopolysaccharide (LPS), which permits modulation of host immune responses by HlyA whilst cell-associated. The effect of HlyA on capsule expression and serum resistance was examined and characterized in this study, with results indicating that perhaps the HlyA-LPS complex interacts with surface capsule. This study is the first to identify haemolysin as a virulence factor promoting resistance to serum in CFT073, acting whilst associated with the cell.

Understanding the relationships between bacteria, their ecological and genomic traits, and their environment is important to elucidate microbial community dynamics and their roles in ecosystem functioning. Here, we examined the relationships between soil properties and bacterial traits within highly managed agricultural soil systems subjected to arable crop rotations or management as permanent grass. We assessed the bacterial communities using metabarcoding and assigned each amplicon trait scores for rRNA copy number, genome size, and guanine-cytosine (GC) content, which are classically associated with potential growth rates and specialization. We also calculated the niche breadth trait of each amplicon as a measure of social ubiquity within the examined samples. Within this soil system, we demonstrated that pH was the primary driver of bacterial traits. The weighted mean trait scores of the samples revealed that bacterial communities associated with soils at lower pH (<7) tended to have larger genomes (potential plasticity), have more rRNA (higher growth rate potential), and are more ubiquitous (have less niche specialization) than the bacterial communities from higher pH soils. Our findings highlight not only the association between pH and bacterial community composition but also the importance of pH in driving community functionality by directly influencing genomic and niche traits.

Little is known about biological soil crust (BSC) formation during the early stages of primary succession following glacial retreat. Here, we report on focused sampling of twelve discrete BSC colonies near the snout of a retreating glacier in the High Arctic and show that BSC colonies had significantly higher 16S and 18S rRNA gene diversity than the simpler communities of bare sediments sampled next to each colony. Surprisingly, the colonies also had a higher degree of community dispersion than the more clustered bare sediment controls. There were only eight 16S amplicons that showed 100% prevalence in all 12 of the colonies, and the three most abundant of these keystone amplicons were cyanobacteria, including a nitrogen fixing Nostoc. The only 18S amplicon common to all colonies was a diatom related to Sellaphora. This prominence of phototrophs indicates that early-successional BSC colonies are being supported by photosynthesis rather than ancient- or aeolian-derived organic matter. Co-occurrence network analysis among the phototrophs and fungi identified several potential early-successional soil lichens. Overall, our fine-scaled sampling revealed new insights into community assembly and function in actual communities of interacting microbes (as opposed to mixed communities in bulk soil samples) during the early stages of primary succession.

This study aimed to develop a probiotic fermented beverage inspired by the traditional Brazilian indigenous beverage Cauim. The beverage was formulated using peanuts and soybeans and fermented using a combination of bacteria and yeast based on traditional methods of Brazilian indigenous cultures. The composition and processing conditions of the beverage were optimized using a Plackett-Burman design and response surface methodology. Strains isolated from indigenous Brazilian fermentations, Pediococcus acidilactici CCMA 0347, and Saccharomyces cerevisiae CCMA 0681, were used in addition to the commercial probiotic Lactobacillus acidophilus (HOWARU^®). The optimized formulation contained 61.2% water-soluble peanut extract, inoculated with 8.00, 6.70, and 5.0 log CFU/ml of P. acidilactici, L. acidophilus, and S. cerevisiae, respectively. The fermented beverage maintained a high level of probiotic cell viability (>10⁷ CFU/ml) over 35 days of storage. The metabolic activity of the microorganisms was sustained throughout storage, mirroring the behavior observed in traditional fermented foods such as Cauim. In addition to high probiotic viability, the beverage presented elevated levels of lactic acid and low pH, indicating the presence of postbiotic components. It also showed nutritional richness in proteins, isoflavones, unsaturated fatty acids, and micronutrients. Sensory analysis demonstrated good acceptance, particularly in appearance and aroma, although further improvements are needed in flavor perception. These results indicate that the optimized plant-based beverage is a promising functional food with probiotic and postbiotic properties, good sensory appeal, and potential to promote health while enhancing the cultural value of Brazilian Indigenous food traditions.

The rise of antibiotic-resistant bacteria is a critical issue across various ecological interfaces, highlighting the need for a One Health approach. Enterococcus spp., known for their ability to acquire and disseminate resistance, serve as an excellent model due to their presence in diverse hosts and environments. This study investigates antimicrobial resistance, biofilm formation capacity, and the efficacy of antibiotics on biofilm biomass reduction in isolates from multiple sources. A total of 197 Enterococcus isolates were used. Antimicrobial resistance was determined using the Kirby-Bauer disc diffusion method, and minimum inhibitory concentrations were tested against vancomycin, tetracycline, and ampicillin. Biofilm formation capacity was assessed, and 10 biofilm-formers were subjected to minimum biofilm inhibitory concentration (MBIC) tests to evaluate biofilm biomass reduction. The results showed high resistance rates to erythromycin (84.5%), ciprofloxacin (59.4%), and tetracycline (44.4%), with moderate resistance to ampicillin (36.2%), chloramphenicol (28%), and vancomycin (24.7%). Biofilm formation was observed in 65% of the isolates, with Enterococcus hirae producing the most biofilm biomass. Vancomycin and ampicillin were more effective in reducing biofilm biomass than tetracycline. Ampicillin-resistant isolates produced more biofilm, suggesting a link between resistance and biofilm formation. This study highlights the complexity of antibiotic-resistant Enterococcus spp. and their biofilms, emphasizing the need for research on One Health.