Lipoteichoic acid from Bacillus subtilis subsp. niger WM: isolation and effects on cell wall autolysis and turnover

Gut microbiota and metabolic modulation by supplementation of polysaccharide-producing Bacillus licheniformis from Tibetan Yaks: A comprehensive multi-omics analysis

Gut microbiota and their metabolic processes depend on the intricate interplay of gut microbiota and their metabolic processes. Bacillus licheniformis, a beneficial food supplement, has shown promising effects on stabilizing gut microbiota and metabolites. However, the precise mechanisms underlying these effects remain elusive. In this study, we investigated the impact of polysaccharide-producing B. licheniformis as a dietary supplement on the gut microbiome and metabolites through a combination of scanning electron microscopy (SEM), histological analysis, high-throughput sequencing (HTS), and metabolomics. Our findings revealed that the B. licheniformis-treated group exhibited significantly increased jejunal goblet cells. Moreover, gut microbial diversity was lower in the treatment group as compared to the control, accompanied by noteworthy shifts in the abundance of specific bacterial taxa. Enrichment of Firmicutes, Lachnospiraceae, and Clostridiales_bacterium contrasted with reduced levels of Campylobacterota, Proteobacteria, Parasutterella, and Helicobacter. Notably, the treatment group showed significant weight gain after 33 days, emphasizing the polysaccharide's impact on host metabolism. Delving into gut metabolomics, we discovered significant alterations in metabolites. Nine metabolites, including olprinone, pyruvic acid, and 2-methyl-3-oxopropanoate, were upregulated, while eleven, including defoslimod and voclosporin were down-regulated, shedding light on phenylpropanoid biosynthesis, tricarboxylic acid cycle (TCA cycle), and the glucagon signaling pathway. This comprehensive multi-omics analysis offers compelling insights into the potential of B. licheniformis as a dietary polysaccharide supplement for gut health and host metabolism, promising significant implications for gut-related issues.

Systematic review of membrane components of gram-positive bacteria responsible as pyrogens for inducing human monocyte/macrophage cytokine release

Fifty years after the elucidation of lipopolysaccharides (LPS, endotoxin) as the principal structure of Gram-negative bacteria activating the human immune system, its Gram-positive counterpart is still under debate. Pyrogen tests based on the human monocyte activation have been validated for LPS detection as an alternative to the rabbit test and, increasingly, the limulus amebocyte lysate test. For full replacement, international validations with non-endotoxin pyrogens are in preparation. Following evidence-based medicine approaches, a systematic review of existing evidence as to the structural nature of the Gram-positive pyrogen was undertaken. For the three major constituents suggested, i.e., peptidoglycan, lipoteichoic acids (LTA), and bacterial lipoproteins (LP), the questions to be answered and a search strategy for relevant literature was developed, starting in MedLine. The evaluation was based on the Koch–Dale criteria for a mediator of an effect. A total of 380 articles for peptidoglycan, 391 for LP, and 285 for LTA were retrieved of which 12, 8, and 24, respectively, fulfilled inclusion criteria. The compiled data suggest that for peptidoglycan two Koch–Dale criteria are fulfilled, four for LTA, and two for bacterial LP. In conclusion, based on the best currently available evidence, LTA is the only substance that fulfills all criteria. LTA has been isolated from a large number of bacteria, results in cytokine release patterns inducible also with synthetic LTA. Reduction in bacterial cytokine induction with an inhibitor for LTA was shown. However, this systematic review cannot exclude the possibility that other stimulatory compounds complement or substitute for LTA in being the counterpart to LPS in some Gram-positive bacteria.

Hydrogen peroxide-dependent DNA release and transfer of antibiotic resistance genes in Streptococcus gordonii

Certain oral streptococci produce H(2)O(2) under aerobic growth conditions to inhibit competing species like Streptococcus mutans. Additionally, H(2)O(2) production causes the release of extracellular DNA (eDNA). eDNA can participate in several important functions: biofilm formation and cell-cell aggregation are supported by eDNA, while eDNA can serve as a nutrient and as an antimicrobial agent by chelating essential cations. eDNA contains DNA fragments of a size that has the potential to transfer genomic information. By using Streptococcus gordonii as a model organism for streptococcal H(2)O(2) production, H(2)O(2)-dependent eDNA release was further investigated. Under defined growth conditions, the eDNA release process was shown to be entirely dependent on H(2)O(2). Chromosomal DNA damage seems to be the intrinsic signal for the release, although only actively growing cells were proficient eDNA donors. Interestingly, the process of eDNA production was found to be coupled with the induction of the S. gordonii natural competence system. Consequently, the production of H(2)O(2) triggered the transfer of antibiotic resistance genes. These results suggest that H(2)O(2) is potentially much more than a simple toxic metabolic by-product; rather, its production could serve as an important environmental signal that facilitates species evolution by transfer of genetic information and an increase in the mutation rate.

Physiological characterization of Streptococcus bovis mutants that can resist 2-deoxyglucose-induced lysis

Streptococcus bovis JB1 does not normally lyse, but stationary phase lysis can be induced by including 2-deoxyglucose (2DG) in the growth medium. Isolates deficient in glucose/2DG phosphotransferase activity (PTS-) also lysed when 2DG was present (Lys+) and this result indicated that 2DG phosphorylation via the PTS was not an obligate requirement for 2DG-induced lysis. Cells and cell walls from 2DG-grown cultures lysed faster when proteinase K was added, but glucose-grown cultures and cell walls were not affected. A lipoteichoic acid (LTA) extract (aqueous phase from hot phenol treatment) from glucose-grown cells inhibited the lysis of 2DG-grown cultures, but a similar extract prepared from 2DG-grown cells was without effect. Thin-layer chromatography and differential staining indicated that wild-type and Lys+ PTS- cells incorporated 2DG into LTA, but lysis-resistant cultures (Lys- PTS+ and Lys- PTS-) did not. LTA from lysis-resistant (Lys- PTS+ and Lys- PTS-) cells grown with glucose and 2DG also prevented 2DG-dependent lysis of the wild-type. LTA could not inhibit degradation of cell walls isolated from 2DG-grown cultures, but LTA inhibited the lysis of Micrococcus lysodeikticus (Micrococcus luteus) cells that were exposed to supernatants from 2DG-grown S. bovis cultures. Group D streptococci (including S. bovis) normally have an alpha-1,2 linked glucose disaccharide (kojibiose) in their LTA, but kojibiose cannot be synthesized from 2DG. This observation suggested that the kojibiose moiety of LTA was involved in autolysin inactivation. Wild-type S. bovis had ATP- as well as PEP-dependent mechanisms of 2DG phosphorylation and one lysis-resistant phenotype (Lys- PTS-) had reduced levels of both activities. However, the Lys- PTS+ phenotype was still able to phosphorylate 2DG via ATP and PEP and this result indicated that some other step of 2DG incorporation into LTA was being inhibited. Based on these results, growth in the presence of 2DG appears to prevent synthesis of normal LTA, which is involved in the regulation of autolytic enzymes.

Correlation of penicillin-induced lysis of Enterococcus faecium with saturation of essential penicillin-binding proteins and release of lipoteichoic acid

Clinical isolates of Enterococcus faecium that had a range of susceptibilities to penicillin were found to differ significantly in their responses to the antibiotic. In the penicillin-susceptible group (MIC, less than or equal to 4 micrograms/ml), the cessation of growth (bacteriostasis) at 10 x the MIC of penicillin appeared to correlate with the inhibition of penicillin-binding protein (PBP) 5*, whereas the onset of lysis (bactericidal effect) at higher antibiotic concentrations (100 x the MIC) was concomitant with the inhibition of the lower-affinity PBP 5. In contrast, in the resistant (MIC, greater than or equal to 8 micrograms/ml) group (in which most of the strains did not contain PBP 5*), the degree of saturation of PBP 5 seemed to determine the physiological response to the antibiotic: low levels of saturation caused growth inhibition, whereas almost complete saturation correlated with lysis. The penicillin-induced cell lysis of both penicillin-susceptible and -resistant strains was attributed, at least in part, to the extensive loss of acylated lipoteichoic acid into the growth medium.

Induction of autolysis in Enterococcus faecalis S-47 by peptide AS-48

In addition to its bactericidal mode of action, the peptide antibiotic AS-48 exhibits a bacteriolytic effect on Enterococcus faecalis S-47 that is associated with autolysin activation. Bacteriolysis induced by the antibiotic can be modulated by addition of EDTA, divalent cations and autolysin activators (trypsin) or inhibitors (cardiolipin), suggesting that topologic regulation of the autolysins is involved in the process. In addition, inhibitors of protein and RNA synthesis interfere markedly with bacteriolysis, as do ionophores and the ATPase inhibitor DCCD, suggesting the participation of an internal messenger in autolysin activation in the presence of AS-48.