Biology subjects

Willdigg, J. R.

Publications and source records attributed to Willdigg, J. R..

2 recordsLinked to original sources

bioRxiv2024

The Bacillus subtilis cell envelope stress-inducible ytpAB operon modulates membrane properties and contributes to bacitracin resistance

Antibiotics that inhibit peptidoglycan synthesis trigger the activation of both specific and general protective responses. {sigma}M responds to diverse antibiotics that inhibit cell wall synthesis. Here, we demonstrate that cell wall inhibiting drugs, such as bacitracin and cefuroxime, induce the {sigma}M-dependent ytpAB operon. YtpA is a predicted hydrolase previously proposed to generate the putative lysophospholipid antibiotic bacilysocin (lysophosphatidylglycerol), and YtpB is the branchpoint enzyme for the synthesis of membrane-localized C35 terpenoids. Using targeted lipidomics we reveal that YtpA is not required for the production of lysophosphatidylglycerol. Nevertheless, ytpA was critical for growth in a mutant strain defective for homeoviscous adaptation due to a lack of genes for the synthesis of branched chain fatty acids and the Des phospholipid desaturase. Consistently, overexpression of ytpA increased membrane fluidity as monitored by fluorescence anisotropy. The ytpA gene contributes to bacitracin resistance in mutants additionally lacking the bceAB or bcrC genes, which directly mediate bacitracin resistance. These epistatic interactions support a model in which {sigma}M-dependent induction of the ytpAB operon helps cells tolerate bacitracin stress, either by facilitating the flipping of the undecaprenyl-phosphate carrier lipid or by impacting the assembly or function of membrane-associated complexes proteins involved in cell wall homeostasis. ImportancePeptidoglycan synthesis inhibitors include some of our most important antibiotics. In Bacillus subtilis, peptidoglycan synthesis inhibitors induce the {sigma}M regulon, which is critical for intrinsic antibiotic resistance. The {sigma}M-dependent ytpAB operon encodes a predicted hydrolase (YtpA) and the enzyme that initiates the synthesis of C35 terpenoids (YtpB). Our results suggest that YtpA is critical in cells defective in homeoviscous adaptation. Further, we find that YtpA functions cooperatively with the BceAB and BcrC proteins in conferring intrinsic resistance to bacitracin, a peptide antibiotic that binds tightly to the UPP lipid carrier that sustains peptidoglycan synthesis.

microbiology↗

bioRxiv2022

A decrease in fatty acid synthesis rescues cells with limited peptidoglycan synthesis capacity

Proper synthesis and maintenance of a multilayered cell envelope is critical for bacterial fitness. However, whether mechanisms exist to coordinate synthesis of the membrane and peptidoglycan layers is unclear. In Bacillus subtilis, synthesis of peptidoglycan (PG) during cell elongation is mediated by an elongasome complex acting in concert with class A PBPs (aPBPs). We previously described mutant strains limited in their capacity for PG synthesis due to a loss of aPBPs and an inability to compensate by upregulation of elongasome function. Growth of these PG-limited cells can be restored by suppressor mutations predicted to decrease membrane synthesis. One suppressor mutation leads to an altered function repressor, FapR*, that functions as a super-repressor and leads to decreased transcription of fatty acid synthesis (FAS) genes. Consistent with fatty acid limitation mitigating cell wall synthesis defects, inhibition of FAS by cerulenin also restored growth of PG-limited cells. Moreover, cerulenin can counteract the inhibitory effect of {beta}-lactams in some strains. These results imply that limiting PG synthesis results in impaired growth, in part, due to an imbalance of PG and cell membrane synthesis and that B. subtilis lacks a robust physiological mechanism to reduce membrane synthesis when PG synthesis is impaired. ImportanceUnderstanding how a bacterium coordinates cell envelope synthesis is essential to fully appreciate how bacteria grow, divide, and resist cell envelope stresses such as {beta}-lactam antibiotics. Balanced synthesis of the peptidoglycan cell wall and the cell membrane is critical for cells to maintain shape, turgor pressure and resist external cell envelope threats. Using Bacillus subtilis, we show that cells deficient in peptidoglycan synthesis can be rescued by compensatory mutations that decrease the synthesis of fatty acids. Further, we show that inhibiting fatty acid synthesis with cerulenin is sufficient to restore growth of cells deficient in peptidoglycan synthesis. Understanding the coordination of cell wall and membrane synthesis may provide insights relevant to antimicrobial treatment.

microbiology↗