Cardiolipin-Containing Lipid Membranes Attract the Bacterial Cell Division Protein DivIVA

Chemokines Kill Bacteria by Binding Anionic Phospholipids without Triggering Antimicrobial Resistance

Classically, chemokines coordinate leukocyte trafficking during immune responses; however, many chemokines have also been reported to possess direct antibacterial activity in vitro. Yet, the bacterial killing mechanism of chemokines and the biochemical properties that define which members of the chemokine superfamily are antimicrobial remain poorly understood. Here we report that the antimicrobial activity of chemokines is defined by their ability to bind phosphatidylglycerol and cardiolipin, two anionic phospholipids commonly found in the bacterial plasma membrane. We show that only chemokines able to bind these two phospholipids kill Escherichia coli and Staphylococcus aureus and that they exert rapid bacteriostatic and bactericidal effects against E. coli with a higher potency than the antimicrobial peptide beta-defensin 3. Furthermore, our data support that bacterial membrane cardiolipin facilitates the antimicrobial action of chemokines. Both biochemical and genetic interference with the chemokine-cardiolipin interaction impaired microbial growth arrest, bacterial killing, and membrane disruption by chemokines. Moreover, unlike conventional antibiotics, E. coli failed to develop resistance when placed under increasing antimicrobial chemokine pressure in vitro. Thus, we have identified cardiolipin and phosphatidylglycerol as novel binding partners for chemokines responsible for chemokine antimicrobial action. Our results provide proof of principle for developing chemokines as novel antibiotics resistant to bacterial antimicrobial resistance mechanisms.

A dynamic duo: Understanding the roles of FtsZ and FtsA for Escherichia coli cell division through in vitro approaches

Bacteria divide by binary fission. The protein machine responsible for this process is the divisome, a transient assembly of more than 30 proteins in and on the surface of the cytoplasmic membrane. Together, they constrict the cell envelope and remodel the peptidoglycan layer to eventually split the cell into two. For Escherichia coli, most molecular players involved in this process have probably been identified, but obtaining the quantitative information needed for a mechanistic understanding can often not be achieved from experiments in vivo alone. Since the discovery of the Z-ring more than 30 years ago, in vitro reconstitution experiments have been crucial to shed light on molecular processes normally hidden in the complex environment of the living cell. In this review, we summarize how rebuilding the divisome from purified components - or at least parts of it - have been instrumental to obtain the detailed mechanistic understanding of the bacterial cell division machinery that we have today.

Insights into the mechanism of mycelium transformation of Streptomyces toxytricini into pellet

Formation of the mycelial pellet in submerged cultivation of Streptomycetes is unwanted in industrial fermentation processes as it imposes mass transfer limitations, changes in the rheology of a medium, and affects the production of secondary metabolites. Though detailed information is not available about the factors involved in regulating mycelial morphology, it is studied that culture conditions and the genetic information of strain play a crucial role. Moreover, the proteomic study has revealed the involvement of low molecular weight proteins such as; DivIVA, FilP, ParA, Scy, and SsgA proteins in apical growth and branching of hyphae, which results in the establishment of the mycelial network. The present study proposes the mechanism of pellet formation of Streptomyces toxytricini (NRRL B-5426) with the help of microscopic and proteomic analysis. The microscopic analysis revealed that growing hyphae contain a bud-like structure behind the apical tip, which follows a certain organized path of growth and branching, which was further converted into the pellet when shake flask to the shake flask inoculation was performed. Proteomic analysis revealed the production of low molecular weight proteins ranging between 20 and 95 kDa, which are involved in apical growth and hyphae branching and can possibly participate in the regulation of pellet morphology.

Cellular mechanics during division of a genomically minimal cell

Genomically minimal cells, such as JCVI-syn3.0 and JCVI-syn3A, offer an empowering framework to study relationships between genotype and phenotype. With a polygenic basis, the fundamental physiological process of cell division depends on multiple genes of known and unknown function in JCVI-syn3A. A physical description of cellular mechanics can further understanding of the contributions of genes to cell division in this genomically minimal context. We review current knowledge on genes in JCVI-syn3A contributing to two physical parameters relevant to cell division, namely, the surface-area-to-volume ratio and membrane curvature. This physical view of JCVI-syn3A may inform the attribution of gene functions and conserved processes in bacterial physiology, as well as whole-cell models and the engineering of synthetic cells.

Binding of DEP domain to phospholipid membranes: More than just electrostatics

Over the past decades an extensive effort has been made to provide a more comprehensive understanding of Wnt signaling, yet many regulatory and structural aspects remain elusive. Among these, the ability of Dishevelled (DVL) protein to relocalize at the plasma membrane is a crucial step in the activation of all Wnt pathways. The membrane binding of DVL was suggested to be mediated by the preferential interaction of its C-terminal DEP domain with phosphatidic acid (PA). However, due to the scarcity and fast turnover of PA, we investigated the role on the membrane association of other more abundant phospholipids. The combined results from computational simulations and experimental measurements with various model phospholipid membranes, demonstrate that the membrane binding of DEP/DVL constructs is governed by the concerted action of generic electrostatics and finely-tuned intermolecular interactions with individual lipid species. In particular, while we confirmed the strong preference for PA lipid, we also observed a weak but non-negligible affinity for phosphatidylserine, the most abundant anionic phospholipid in the plasma membrane, and phosphatidylinositol 4,5-bisphosphate. The obtained molecular insight into DEP-membrane interaction helps to elucidate the relation between changes in the local membrane composition and the spatiotemporal localization of DVL and, possibly, other DEP-containing proteins.