A coating of lipoproteins provides a stabilizing environment on the inner membrane of spores.

A new study by M. J. Flores, K.

Spore germination receptors - a new paradigm.

David Rudner and his team (Gao et al.) predict a pentameric structure for the GerA alanine-responsive germination receptor of Bacillus subtilis and demonstrate that it behaves as a nutrient-gated ion channel, finally establishing a function for this novel family of receptors and focussing research on early ion movements in germination.

Genetic Suppression Meets Structure Prediction: Probing a Spore Germination Receptor Complex.

Despite the thousands of spore germinant receptor operons identified in genomes of bacilli and clostridia, understanding how the three essential receptor components act as a signal transduction machine in germination remains limited. The paper by Amon et al. in this issue uses the classical genetic approach of suppression to define a region of likely interaction between the GerAA and GerAB proteins: it provides a first glimpse into potential events within the receptor complex (J.

Architecture and Self-Assembly of Clostridium sporogenes and Clostridium botulinum Spore Surfaces Illustrate a General Protective Strategy across Spore Formers.

Spores, the infectious agents of many , are remarkably resilient cell forms. Even distant relatives can have similar spore architectures although some display unique features; they all incorporate protective proteinaceous envelopes. We previously found that spores can achieve these protective properties through extensive disulfide cross-linking of self-assembled arrays of cysteine-rich proteins.

Proteins YlaJ and YhcN contribute to the efficiency of spore germination in Bacillus subtilis.

The YlaJ and YhcN spore lipoproteins of Bacillus subtilis contain a common domain, and are of unknown function. Homologues of YlaJ or YhcN are widespread in Bacilli and are also encoded in those Clostridia that use cortex lytic enzymes SleB and CwlJ for cortex hydrolysis during germination. In B.

Molecular tiling on the surface of a bacterial spore - the exosporium of the Bacillus anthracis/cereus/thuringiensis group.

Bacteria of the genera Bacillus and Clostridium form highly resistant spores, which in the case of some pathogens act as the infectious agents. An exosporium forms the outermost layer of some spores; it plays roles in protection, adhesion, dissemination, host targeting in pathogens and germination control. The exosporium of the Bacillus cereus group, including the anthrax pathogen, contains a 2D-crystalline basal layer, overlaid by a hairy nap.

Characterization of the spore surface and exosporium proteins of Clostridium sporogenes; implications for Clostridium botulinum group I strains.

Clostridium sporogenes is a non-pathogenic close relative and surrogate for Group I (proteolytic) neurotoxin-producing Clostridium botulinum strains. The exosporium, the sac-like outermost layer of spores of these species, is likely to contribute to adhesion, dissemination, and virulence. A paracrystalline array, hairy nap, and several appendages were detected in the exosporium of C.

Spore Germination.

Despite being resistant to a variety of environmental insults, the bacterial endospore can sense the presence of small molecules and respond by germinating, losing the specialized structures of the dormant spore, and resuming active metabolism, before outgrowing into vegetative cells. Our current level of understanding of the spore germination process in bacilli and clostridia is reviewed, with particular emphasis on the germinant receptors characterized in Bacillus subtilis, Bacillus cereus, and Bacillus anthracis. The recent evidence for a local clustering of receptors in a "germinosome" would begin to explain how signals from different receptors could be integrated.

Surface architecture of endospores of the Bacillus cereus/anthracis/thuringiensis family at the subnanometer scale.

Bacteria of the Bacillus cereus family form highly resistant spores, which in the case of the pathogen B. anthracis act as the agents of infection. The outermost layer, the exosporium, enveloping spores of the B.

YwdL in Bacillus cereus: its role in germination and exosporium structure.

In members of the Bacillus cereus group the outermost layer of the spore is the exosporium, which interacts with hosts and the environment. Efforts have been made to identify proteins of the exosporium but only a few have so far been characterised and their role in determining spore architecture and spore function is still poorly understood. We have characterised the exosporium protein, YwdL.

Effect of amino acid substitutions in the GerAA protein on the function of the alanine-responsive germinant receptor of Bacillus subtilis spores.

Spores of Bacillus subtilis require the GerAA, GerAB, and GerAC receptor proteins for L-alanine-induced germination. Mutations in gerAA, both random and site directed, result in phenotypes that identify amino acid residues important for receptor function in broad terms. They highlight the functional importance of two regions in the central, integral membrane domain of GerAA.

Amino acid residues in the GerAB protein important in the function and assembly of the alanine spore germination receptor of Bacillus subtilis 168.

The paradigm gerA operon is required for endospore germination in response to c-alanine as the sole germinant, and the three protein products, GerAA, GerAB, and GerAC are predicted to form a receptor complex in the spore inner membrane. GerAB shows homology to the amino acid-polyamine-organocation (APC) family of single-component transporters and is predicted to be an integral membrane protein with 10 membrane-spanning helices. Site-directed mutations were introduced into the gerAB gene at its natural location on the chromosome.

Localization of the GerD spore germination protein in the Bacillus subtilis spore.

The GerD protein of Bacillus subtilis is required for efficient spore germination in l-alanine, and for germination in the alternative germinant combination of amino acids plus sugars. Only germination via nutrient receptors is affected in the mutant. The GerD protein is predicted to be a lipoprotein that is produced in the forespore compartment of the sporulating cell.

The Bacillus cereus GerN and GerT protein homologs have distinct roles in spore germination and outgrowth, respectively.

The GerT protein of Bacillus cereus shares 74% amino acid identity with its homolog GerN. The latter is a Na(+)/H(+)-K(+) antiporter that is required for normal spore germination in inosine. The germination properties of single and double mutants of B.

Structure of the exosporium and sublayers of spores of the Bacillus cereus family revealed by electron crystallography.

We report on the first step in mapping out the spatial location of structural proteins within the exosporium, namely a description of its three-dimensional architecture. Using electron microscopy and image analysis, we have characterized crystalline fragments from the exosporium of Bacillus cereus, B. thuringiensis and B.

SigM-responsive genes of Bacillus subtilis and their promoters.

Promoters of nine Bacillus subtilis genes (bcrC, yacK, ydaH, yfnI, yjbD, ypbG, ypuA, yraA, and ysxA), all responsive to artificially induced increases in the stress-responsive extracytoplasmic function sigma factor, SigM, were mapped by rapid amplification of cDNA ends-PCR. The resulting promoter consensus suggests that overlapping control by SigX or SigW is common.

ExsY and CotY are required for the correct assembly of the exosporium and spore coat of Bacillus cereus.

The exosporium-defective phenotype of a transposon insertion mutant of Bacillus cereus implicated ExsY, a homologue of B. subtilis cysteine-rich spore coat proteins CotY and CotZ, in assembly of an intact exosporium. Single and double mutants of B.

The ExsA protein of Bacillus cereus is required for assembly of coat and exosporium onto the spore surface.

The outermost layer of spores of the Bacillus cereus family is a loose structure known as the exosporium. Spores of a library of Tn917-LTV1 transposon insertion mutants of B. cereus ATCC 10876 were partitioned into hexadecane; a less hydrophobic mutant that was isolated contained an insertion in the exsA promoter region.

Identification of proteins in the exosporium of Bacillus anthracis.

Spores of Bacillus anthracis, the causative agent of anthrax, possess an exosporium. As the outer surface layer of these mature spores, the exosporium represents the primary contact surface between the spore and environment/host and is a site of spore antigens. The exosporium was isolated from the endospores of the B.

Bacterial spore germination and protein mobility.

Fluorescence recovery after photobleaching (FRAP) of green fluorescent protein (GFP) has been used to report on protein mobility in single spores. Proteins found in dormant Bacillus spores are not mobile; however, mobility is restored when germination occurs and the core rehydrates. Spores of a cwlD mutant, in which the cortex is resistant to hydrolysis, are able to complete the earliest stages of germination in response to a specific germinant stimulus; in these circumstances, the protein in the spore remains immobile.

Mutational loss of a K+ and NH4+ transporter affects the growth and endospore formation of alkaliphilic Bacillus pseudofirmus OF4.

A putative transport protein (Orf9) of alkaliphilic Bacillus pseudofirmus OF4 belongs to a transporter family (CPA-2) of diverse K+ efflux proteins and cation antiporters. Orf9 greatly increased the concentration of K+ required for growth of a K+ uptake mutant of Escherichia coli. The cytoplasmic K+ content of the cells was reduced, consistent with an efflux mechanism.

SigM, an extracytoplasmic function sigma factor of Bacillus subtilis, is activated in response to cell wall antibiotics, ethanol, heat, acid, and superoxide stress.

The extracytoplasmic function sigma M of Bacillus subtilis is required for normal cell growth under salt stress. It is expressed maximally during exponential growth and is further induced by the addition of 0.7 M NaCl.

Genes of Bacillus cereus and Bacillus anthracis encoding proteins of the exosporium.

The exosporium is the outermost layer of spores of Bacillus cereus and its close relatives Bacillus anthracis and Bacillus thuringiensis. For these pathogens, it represents the surface layer that makes initial contact with the host. To date, only the BclA glycoprotein has been described as a component of the exosporium; this paper defines 10 more tightly associated proteins from the exosporium of B.

Analysis of spore cortex lytic enzymes and related proteins in Bacillus subtilis endospore germination.

The location and function of recognized cortex-lytic enzymes of Bacillus subtilis have been explored, and the involvement in germination of a number of related proteins tested. The SleB and CwlJ proteins are cortex-lytic enzymes, partially redundant in function, that are required together for effective cortex hydrolysis during B. subtilis spore germination.

Germination of Bacillus cereus spores in response to L-alanine and to inosine: the roles of gerL and gerQ operons.

Bacillus cereus 569 (ATCC 10876) endospores germinate in response to inosine or L-alanine, the most rapid germination response being elicited by a combination of these germinants. The gerI operon has already been characterized as a homologue of the gerA spore-germination receptor family of operons found in all Bacillus spp. examined; the primary defect in gerI mutant spores is in the inosine germination response, although spores were also slower to germinate in L-alanine.