A Cardiolipin-Deficient Mutant of Rhodobacter sphaeroides Has an Altered Cell Shape and Is Impaired in Biofilm Formation

Abstract

Cell shape has been suggested to play an important role in the regulation of bacterial attachment to surfaces and the formation of communities associated with surfaces. We found that a cardiolipin synthase (⌬cls) mutant of the rod-shaped bacterium Rhodobacter sphaeroides-in which synthesis of the anionic, highly curved phospholipid cardiolipin (CL) is reduced by 90%-produces ellipsoid-shaped cells that are impaired in biofilm formation. Reducing the concentration of CL did not cause significant defects in R. sphaeroides cell growth, swimming motility, lipopolysaccharide and exopolysaccharide production, surface adhesion protein expression, and membrane permeability. Complementation of the CL-deficient mutant by ectopically expressing CL synthase restored cells to their rod shape and increased biofilm formation. Treating R. sphaeroides cells with a low concentration (10 g/ml) of the small-molecule MreB inhibitor S-(3,4-dichlorobenzyl)isothiourea produced ellipsoid-shaped cells that had no obvious growth defect yet reduced R. sphaeroides biofilm formation. This study demonstrates that CL plays a role in R. sphaeroides cell shape determination, biofilm formation, and the ability of the bacterium to adapt to its environment. IMPORTANCEMembrane composition plays a fundamental role in the adaptation of many bacteria to environmental stress. In this study, we build a new connection between the anionic phospholipid cardiolipin (CL) and cellular adaptation in Rhodobacter sphaeroides. We demonstrate that CL plays a role in the regulation of R. sphaeroides morphology and is important for the ability of this bacterium to form biofilms. This study correlates CL concentration, cell shape, and biofilm formation and provides the first example of how membrane composition in bacteria alters cell morphology and influences adaptation. This study also provides insight into the potential of phospholipid biosynthesis as a target for new chemical strategies designed to alter or prevent biofilm formation. Many bacteria have evolved mechanisms of community-based living based on attachment to surfaces and growth into biofilms. Biofilm formation occurs through several stages. In the first stage, bacterial cells attach to surfaces, replicate, and accumulate to form multilayered cell communities. During biofilm maturation, bacteria secrete a layer of extracellular polymeric substances that encapsulates cells and protects them from environmental stress. At a later stage, planktonic bacterial cells are released into the bulk fluid, attach to new surfaces, replicate, and seed the formation of new biofilms. Biofilms are a central mechanism that bacteria use to adapt to changes in their environment, are prevalent in ecology, and present challenges in industrial applications and medicine due to biofouling and antibiotic resistance (1-3). For example, the North American Centers for Disease Control and Prevention estimates that 65% of all human infections by bacteria involve biofilms (4).The shape of bacterial cells has been hypothesized to ...

Effect of thermal control of dry fomites on regulating the survival of human pathogenic bacteria responsible for nosocomial infections

“…High-touch dry surfaces are invariably contaminated with S. aureus because this organism is a ubiquitous inhabitant of the human body, and it is therefore crucial to understand its dynamics on dry surfaces. Cardiolipin is a membrane component that enhances stress tolerance, thereby maintaining bacterial viability [43][44][45], and several studies have shown that cardiolipin is involved in biofilm formation [46,47]. We therefore assessed whether the presence of cardiolipin affected the survival of E. coli on dry surfaces, but no impact was detected indicating that other factors may be involved.…”

Two Distinct Cardiolipin Synthases Operate in Agrobacterium tumefaciens

“…Anionic phospholipids, like CL and PG, are crucial for cell cycle, osmotic stress and cell morphology in different bacteria [ 3 , 10 , 11 , 46 ]. To determine the physiological role of CL in A .…”

“…A recent study revealed that CL deficiency in R . sphaeroides leads to defects in biofilm formation and produces ellipsoidal-shaped cells, while growth remained unaffected [ 11 ]. Likewise, a Pseudomonas putida cls mutant is smaller in size compared to wild-type cells and exhibits increased sensitivity to several antibiotics but displays no growth defect [ 52 ].…”

“…In Staphylococcus aureus , prolonged survival under high-salinity conditions depends on the presence of CL [ 10 ]. In Rhodobacter sphaeroides , CL deficiency leads to altered cell morphology and negatively affects biofilm formation [ 11 ]. However, despite its broad impact on cell physiology, CL does not appear to be essential for bacterial survival, since loss of CL mostly results in rather mild phenotypes.…”

Bridging the Timescales of Single-Cell and Population Dynamics

“…Typically, the coefficient of variation (COV, defined as the ratio of the standard deviation to the mean) of division times is 10%-30% [2][3][4][5][6][7][8][9][10][11][12][13][14]. Using recent advances in single-cell technologies, it is possible to characterize these fluctuations with exquisite precision for large ensembles of statistically identical cells [2].…”