CerM and Its Antagonist CerN Are New Components of the Quorum Sensing System in Cereibacter sphaeroides, Signaling to the CckA/ChpT/CtrA System.

Cereibacter sphaeroides has a quorum sensing (QS) system that has been partially characterized. Using a bioinformatic approach, six LuxR homologs and one homolog of the acylhomoserine lactone synthase were identified in this bacterium, including the previously characterized CerR and CerI proteins. This study focused on determining the roles of two LuxR homologs, CerM and CerN.

Rotation of the Fla2 flagella of Cereibacter sphaeroides requires the periplasmic proteins MotK and MotE that interact with the flagellar stator protein MotB2.

The bacterial flagellum is a complex structure formed by more than 25 different proteins, this appendage comprises three conserved structures: the basal body, the hook and filament. The basal body, embedded in the cell envelope, is the most complex structure and houses the export apparatus and the motor. In situ images of the flagellar motor in different species have revealed a huge diversity of structures that surround the well-conserved periplasmic components of the basal body.

A new type of phasin characterized by the presence of a helix-hairpin-helix domain is required for normal polyhydroxybutyrate accumulation and granule organization in Caulobacter crescentus.

Bacteria frequently store excess carbon in hydrophobic granules of polyhydroxybutyrate (PHB) that in some growth conditions can occupy most of the cytoplasmic space. Different types of proteins associate to the surface of the granules, mainly enzymes involved in the synthesis and utilization of the reserve polymer and a diverse group of proteins known as phasins. Phasins have different functions, among which are regulating the size and number of the granules, modulating the activity of the granule-associated enzymes and helping in the distribution of the granules inside the cell.

The Histidine Kinase CckA Is Directly Inhibited by a Response Regulator-like Protein in a Negative Feedback Loop.

In alphaproteobacteria, the two-component system (TCS) formed by the hybrid histidine kinase CckA, the phosphotransfer protein ChpT, and the response regulator CtrA is widely distributed. In these microorganisms, this system controls diverse functions such as motility, DNA repair, and cell division. In and , CckA is regulated by the pseudo- histidine kinase DivL, and the response regulator DivK.

Bacterial cell wall quantification by a modified low-volume Nelson-Somogyi method and its use with different sugars.

The study of peptidoglycan-binding proteins frequently requires in vitro binding assays, in which the isolated peptidoglycan used as a substrate must be carefully quantified. Here, we describe an easy and sensitive assay for peptidoglycan quantification based on a modified Nelson-Somogyi reducing sugar assay. We report the response of this assay to different common sugars and adapt its use to peptidoglycan samples subjected to acid hydrolysis.

Changes in fluidity of the E. coli outer membrane in response to temperature, divalent cations and polymyxin-B show two different mechanisms of membrane fluidity adaptation.

The outer membrane (OM) is an essential component of the Gram-negative bacterial cell envelope. Restricted diffusion of integral OM proteins and lipopolysaccharide (LPS) that constitute the outer leaflet of the OM support a model in which the OM is in a semi-crystalline state. The low fluidity of the OM has been suggested to be an important property of this membrane that even contributes to cell rigidity.

Modulation of the Enzymatic Activity of the Flagellar Lytic Transglycosylase SltF by Rod Components and the Scaffolding Protein FlgJ in .

Macromolecular cell-envelope-spanning structures such as the bacterial flagellum must traverse the cell wall. Lytic transglycosylase enzymes are capable of enlarging gaps in the peptidoglycan meshwork to allow the efficient assembly of supramolecular complexes. In the periplasmic space, the assembly of the flagellar rod requires the scaffold protein FlgJ, which includes a muramidase domain in the canonical models Salmonella enterica and Escherichia coli.

The periplasmic component of the DctPQM TRAP-transporter is part of the DctS/DctR sensory pathway in .

can use C4-dicarboxylic acids to grow heterotrophically or photoheterotropically, and it was previously demonstrated in that the DctPQM transporter system is essential to support growth using these organic acids under heterotrophic but not under photoheterotrophic conditions. In this work we show that in this transporter system is essential for photoheterotrophic and heterotrophic growth, when C4-dicarboxylic acids are used as a carbon source. We also found that over-expression of is detrimental for photoheterotrophic growth in the presence of succinic acid in the culture medium.

Living in a Foster Home: The Single Subpolar Flagellum Fla1 of .

is an α-proteobacterium that has the particularity of having two functional flagellar systems used for swimming. Under the growth conditions commonly used in the laboratory, a single subpolar flagellum that traverses the cell membrane, is assembled on the surface. This flagellum has been named Fla1.

The CtrA Regulon of Rhodobacter sphaeroides Favors Adaptation to a Particular Lifestyle.

Activation of the two-component system formed by CckA, ChpT, and CtrA (kinase, phosphotransferase, and response regulator, respectively) in does not occur under the growth conditions commonly used in the laboratory. However, it is possible to isolate a gain-of-function mutant in CckA that turns the system on. Using massive parallel transcriptome sequencing (RNA-seq), we identified 321 genes that are differentially regulated by CtrA.

Establishment of a Protein Concentration Gradient in the Outer Membrane Requires Two Diffusion-Limiting Mechanisms.

OmpA-like proteins are involved in the stabilization of the outer membrane, resistance to osmotic stress, and pathogenesis. In , OmpA2 forms a physiologically relevant concentration gradient that forms by an uncharacterized mechanism, in which the gradient orientation depends on the position of the gene locus. This suggests that OmpA2 is synthesized and translocated to the periplasm close to the position of the gene and that the gradient forms by diffusion of the protein from this point.

Characterization of FlgP, an Essential Protein for Flagellar Assembly in .

The flagellar lipoprotein FlgP has been identified in several species of bacteria, and its absence provokes different phenotypes. In this study, we show that in the alphaproteobacterium , a Δ mutant is unable to assemble the hook and the filament. In contrast, the membrane/supramembrane (MS) ring and the flagellar rod appear to be assembled.

Architecture of divergent flagellar promoters controlled by CtrA in Rhodobacter sphaeroides.

Background: Rhodobacter sphaeroides has two sets of flagellar genes, fla1 and fla2, that are responsible for the synthesis of two different flagellar structures. The expression of the fla2 genes is under control of CtrA. In several α-proteobacteria CtrA is also required for the expression of the flagellar genes, but the architecture of CtrA-dependent promoters has only been studied in detail in Caulobacter crescentus.

Biochemical and Phylogenetic Study of SltF, a Flagellar Lytic Transglycosylase from Rhodobacter sphaeroides.

In this work, we have characterized the soluble lytic transglycosylase (SltF) from that interacts with the scaffolding protein FlgJ in the periplasm to open space at the cell wall peptidoglycan heteropolymer for the emerging rod. The characterization of the genetic context of and s in alphaproteobacteria shows that these two separate genes coexist frequently in a flagellar gene cluster. Two domains of unknown function in SltF were studied, and the results show that the deletion of a 17-amino-acid segment near the N terminus does not show a recognizable phenotype, whereas the deletion of 47 and 95 amino acids of the C terminus of SltF disrupts the interaction with FlgJ without affecting the transglycosylase catalytic activity of SltF.

Purification of Fla2 Flagella of Rhodobacter sphaeroides.

The photosynthetic bacterium R. sphaeroides expresses two flagellar systems that are encoded by two complete gene clusters that have distinct phylogenetic origins. The isolation and purification of the Filament-Hook Basal Body (F-HBB) or the Hook Basal Body (HBB) structure is a troublesome task given the complexity of this nano-machine that is composed of multiple loosely bound substructures that can be lost during the isolation and purification procedure.

A New Essential Cell Division Protein in Caulobacter crescentus.

Bacterial cell division is a complex process that relies on a multiprotein complex composed of a core of widely conserved and generally essential proteins and on accessory proteins that vary in number and identity in different bacteria. The assembly of this complex and, particularly, the initiation of constriction are regulated processes that have come under intensive study. In this work, we characterize the function of DipI, a protein conserved in and that is essential in Our results show that DipI is a periplasmic protein that is recruited late to the division site and that it is required for the initiation of constriction.

The Master Regulators of the Fla1 and Fla2 Flagella of Rhodobacter sphaeroides Control the Expression of Their Cognate CheY Proteins.

is an alphaproteobacterium that has two complete sets of flagellar genes. The set was acquired by horizontal transfer from an ancestral gammaproteobacterium and is the only set of flagellar genes that is expressed during growth under standard laboratory conditions. The products of these genes assemble a single, subpolar flagellum.

Biochemical Characterization of the Flagellar Rod Components of Rhodobacter sphaeroides: Properties and Interactions.

Unlabelled: The flagellar basal body is a rotary motor that spans the cytoplasmic and outer membranes. The rod is a drive shaft that transmits torque generated by the motor through the hook to the filament that propels the bacterial cell. The assembly and structure of the rod are poorly understood.

Structural Characterization of the Fla2 Flagellum of Rhodobacter sphaeroides.

Unlabelled: Rhodobacter sphaeroides is a free-living alphaproteobacterium that contains two clusters of functional flagellar genes in its genome: one acquired by horizontal gene transfer (fla1) and one that is endogenous (fla2). We have shown that the Fla2 system is normally quiescent and under certain conditions produces polar flagella, while the Fla1 system is always active and produces a single flagellum at a nonpolar position. In this work we purified and characterized the structure and analyzed the composition of the Fla2 flagellum.

Induction of the lateral flagellar system of Vibrio shilonii is an early event after inhibition of the sodium ion flux in the polar flagellum.

In this study, we show the induction of lateral flagella by the action of the sodium channel blocker phenamil, in the marine bacterium Vibrio shilonii, a coral pathogen that causes bleaching. We analyzed the growth and morphology of cells treated with phenamil. A time course analysis showed that after 30 min of exposure to the sodium channel blocker, lateral flagella were present and could be detected by electron microscopy.

The flagellar set Fla2 in Rhodobacter sphaeroides is controlled by the CckA pathway and is repressed by organic acids and the expression of Fla1.

Rhodobacter sphaeroides has two different sets of flagellar genes. Under the growth conditions commonly used in the laboratory, the expression of the fla1 set is constitutive, whereas the fla2 genes are not expressed. Phylogenetic analyses have previously shown that the fla1 genes were acquired by horizontal transfer from a gammaproteobacterium and that the fla2 genes are endogenous genes of this alphaproteobacterium.

A distant homologue of the FlgT protein interacts with MotB and FliL and is essential for flagellar rotation in Rhodobacter sphaeroides.

In this work, we describe a periplasmic protein that is essential for flagellar rotation in Rhodobacter sphaeroides. This protein is encoded upstream of flgA, and its expression is dependent on the flagellar master regulator FleQ and on the class III flagellar activator FleT. Sequence comparisons suggest that this protein is a distant homologue of FlgT.

A novel component of the Rhodobacter sphaeroides Fla1 flagellum is essential for motor rotation.

Here we describe a novel component essential for flagellar rotation in Rhodobacter sphaeroides. This protein is encoded by motF (RSP_0067), the first gene of a predicted transcriptional unit which contains two hypothetical genes. Sequence analysis indicated that MotF is a bitopic membrane-spanning protein.