Biology subjects

Muhammed, M. K.

Publications and source records attributed to Muhammed, M. K..

2 recordsLinked to original sources

bioRxiv2023

Ex-Lactobacillus Strains with Intrinsic Propensity to Stabilize Pickering Oil-in-Water Emulsions

Knowledge of surface characteristics is a major step in the evaluation of bacterial cells for potential use as Pickering emulsion stabilizers. Here, the cell surface characteristics of 31 strains of the ex-Lactobacillus genus were studied with the aim of evaluating their intrinsic abilities to serve as Pickering stabilizers of oil-in-water emulsions. About 77.42% of the tested strains demonstrated relatively highly negative zeta potential (-43.76 mV [≤] zeta potential [≤] -19.23 mV), while [~]58% of the strains demonstrated high cell surface hydrophobicity (microbial adhesion to hexadecane or MATH [≥] 30%). By combining these findings, four different cell surface features were defined (I, II, II and IV). Strains mainly demonstrated the type I surface feature ([~]45%), with most expressing strongly negative zeta potential and high surface hydrophobicity (zeta potential < -15 mV and MATH [≥] 30%, respectively). It appeared that the abundance of negative charge on the surfaces of ex-Lactobacillus cells positively influences surface hydrophobicity. Assessment of intrinsic Pickering stabilization potential using 12 selected strains indicated that four strains showed profound droplet size stability. At least one strain was observed to have natural propensity to form relativley compact and small emulsion droplets (63{+/-}3 {micro}m), leading to enhanced firmness and storage stability of the Pickering emulsions.

microbiology↗

bioRxiv2022

CRISPR-Cas provides limited phage immunity to a prevalent gut bacterium in gnotobiotic mice

Many prokaryotes harbor the adaptive CRISPR-Cas system, which stores small nucleotide fragments from previous invasions of nucleic acids via viruses or plasmids. This molecular archive blocks further invaders carrying identical or similar nucleotide sequences. However, very few of these systems have been experimentally confirmed to be active in gut bacteria. Here, we experimentally demonstrate that the type I-C CRISPR-Cas system of the prevalent gut bacterium Eggerthella lenta can specifically target and cleave foreign DNA in vitro by using a plasmid transformation assay. We also show that the CRISPR-Cas system acquires new immunities (spacers) from the genome of a virulent E. lenta phage using traditional phage-assays in vitro but also in vivo using gnotobiotic (GB) mice. An increased number of spacer acquisition events were observed when E. lenta was exposed to a low multiplicity of infection in vitro, and three phage genes were found to contain protospacer hotspots. Interestingly, much less new spacer acquisitions were detected in vivo than in vitro. Longitudinal analysis of phage-bacteria interactions showed sustained coexistence in the gut of GB mice, with phage abundance being approximately one log higher than the bacteria. Our findings show that while the type I-C CRISPR-Cas system is active in vitro and in vivo, a highly virulent phage in vitro was still able co-exist with its bacterial host in vivo. Taken altogether, our results suggest that the CRISPR-Cas defense system of E. lenta provides only partial immunity in the gut.

microbiology↗