Biology subjects

Wongdontree, P.

Publications and source records attributed to Wongdontree, P..

3 recordsLinked to original sources

bioRxiv2026

Two temperature-dependent membrane fluidity regimes in Gram-positive bacteria

It is widely accepted that bacterial cells maintain a constant membrane fluidity in response to temperature changes. This process, known as membrane fluidity homeostasis, occurs through remodeling of plasma membrane composition. We tested this using an assay based on total internal reflection-fluorescence correlation spectroscopy (TIR-FCS) that directly quantifies membrane fluidity as the diffusion speed of a membrane marker in Bacillus subtilis and two other Gram-positive bacteria, Streptococcus pneumoniae and Staphylococcus aureus, across a temperature range of 20{degrees}C to 37{degrees}C. Instead of the expected constant membrane fluidity, we identified a two-component regime: membrane fluidity is maintained at low temperatures (<26{degrees}C), but freely increases at higher temperatures. Significance statementTemperature changes affect the physical properties of the bacterial plasma membrane. Typically, with a reduction in temperature comes a loss of membrane fluidity. It is known that bacteria like Bacillus subtilis adapt their membrane composition when this happens, and it was thought to maintain membrane fluidity constant. We found that this is not true: fluidity is maintained only in a low (<26{degrees}C) temperature regime, while at higher temperatures fluidity is not maintained. We found this to be true for several Gram+ bacteria.

biophysics↗

bioRxiv2024

Metabolic rerouting by gain-of-function mutations overcomes plsX essentiality in Staphylococcus aureus

Phospholipids are essential components of most cell membranes. In Staphylococcus aureus, PlsX acyltransferase is considered indispensable for initiating phospholipid synthesis, unless exogenous fatty acids (FAs) are available to bypass this requirement. We report that S. aureus can capture internal FA sources to overcome PlsX essentiality in a {Delta}plsX mutant via point mutations in either of two genes: fabF, which encodes the FA synthesis enzyme 3-oxoacyl-(acyl-carrier-protein) synthase II, or fadM, which encodes an understudied bifunctional acyl-CoA thioesterase and ACP binding protein. Despite growth rescue, both {Delta}plsX suppressors differ from the parental strain by producing phospholipids with shortened FA lengths suggesting that both suppressors lead to premature FA release during synthesis. Additionally, both suppressors display increased sensitivity to {beta}-lactam antibiotics. The similar behavior of both suppressors led us to show that fabF suppressors require the presence of fadM, indicative of FabF-FadM cooperation. We propose that reduced processivity of FabF suppressor variants, or greater availability of FadM for ACP binding in FadM variants, facilitates FA release from FabF-acyl-ACP intermediates. A FabF-FadM relay leading to FA release may contribute to homeostasis between FASII and phospholipid synthesis pathways. SignificancePhospholipids are vital cell membrane components. The essential Staphylococcus aureus phospholipid synthesis enzyme PlsX uses acyl-ACP, the end-product of fatty acid (FA) synthesis (FASII), to initiate phospholipid production. Despite its central role, PlsX can be substituted by exogenous FAs whose phosphorylation yields the same product. We discovered that without FA supplementation, mutants arise that rescue growth, indicating that internal FAs are released. Mutations occurred in either FabF, a FASII enzyme, or in FadM, an incompletely characterized protein. Our analyses give evidence that FabF and FadM proteins cooperate, and facilitate FA availability when either protein is mutated. We propose that in normal conditions, FadM might act as an "overflow valve" by releasing FAs from the FabF intermediate, which prevents buildup of FASII intermediates, and ensures FA-phospholipid balance. Remarkably, while this pathway rescues S. aureus growth, it sensitizes the MRSA strain to {beta}-lactam antibiotics.

microbiology↗

bioRxiv2022

Inverse correlation between stress response and virulence factor expression in FASII antibiotic-adapted Staphylococcus aureus and consequences for infection

Antibiotics inhibiting the fatty acid synthesis (FASII) pathway of the major pathogen Staphylococcus aureus reach their enzyme targets, but bacteria continue growth by using environmental fatty acids (eFAs) to produce phospholipids. We assessed how extreme changes in membrane phospholipids provoked by FASII-antibiotics affect global S. aureus physiology. Anti-FASII provoked massive lasting expression changes without genomic rearrangements. Several regulators, rather than one master switch, contributed to the timing of anti-FASII adaptation. Numerous virulence and adhesion factors showed decreased levels and/or activity. Conversely, stress response protein levels increased, and correlated with greater tolerance to peroxides. Notably, peroxide priming stimulated eFA incorporation efficiency and facilitated adaptation to FASII inhibition. These findings establish a link between oxidative stress and FA incorporation. Consistent with major shift in protein expression, anti-FASII-adapted S. aureus killed an insect host more slowly but continued multiplying. Thus, while anti-FASII-adapted populations are less equipped to damage the host, they may be better fit for long term survival, and could constitute a reservoir for re-infection.

microbiology↗