How to get (a)round: mechanisms controlling growth and division of coccoid bacteria.

Bacteria come in a range of shapes, including round, rod-shaped, curved and spiral cells. This morphological diversity implies that different mechanisms exist to guide proper cell growth, division and chromosome segregation. Although the majority of studies on cell division have focused on rod-shaped cells, the development of new genetic and cell biology tools has provided mechanistic insight into the cell cycles of bacteria with different shapes, allowing us to appreciate the underlying molecular basis for their morphological diversity. In this Review, we discuss recent progress that has advanced our knowledge of the complex mechanisms for chromosome segregation and cell division in bacteria which have, deceptively, the simplest possible shape: the cocci.

Tied down: tethering redox proteins to the outer membrane in Neisseria and other genera.

Typically, the redox proteins of respiratory chains in Gram-negative bacteria are localized in the cytoplasmic membrane or in the periplasm. An alternative arrangement appears to be widespread within the betaproteobacterial genus Neisseria, wherein several redox proteins are covalently associated with the outer membrane. In the present paper, we discuss the structural properties of these outer membrane redox proteins and the functional consequences of this attachment. Several tethered outer membrane redox proteins of Neisseria contain a weakly conserved repeated structure between the covalent tether and the redox protein globular domain that should enable the redox cofactor-containing domain to extend from the outer membrane, across the periplasm and towards the inner membrane. It is argued that the constraints imposed on the movement and orientation of the globular domains by these tethers favours the formation of electron-transfer complexes for entropic reasons. The attachment to the outer membrane may also affect the exposure of the host to redox proteins with a moonlighting function in the host-microbe interaction, thus affecting the host response to Neisseria infection. We identify putative outer membrane redox proteins from a number of other bacterial genera outside Neisseria, and suggest that this organizational arrangement may be more common than previously recognized.

Cellular adhesion molecules as targets for bacterial infection.

A large number of bacterial pathogens targets cell adhesion molecules to establish an intimate contact with host cells and tissues. Members of the integrin, cadherin and immunoglobulin-related cell adhesion molecule (IgCAM) families are frequently recognized by specific bacterial surface proteins. Binding can trigger bacterial internalization following cytoskeletal rearrangements that are initiated upon receptor clustering. Moreover, signals emanating from the occupied receptors can result in cellular responses such as gene expression events that influence the phenotype of the infected cell. This review will address recent advances in our understanding of bacterial engagement of cellular adhesion molecules by discussing the binding of integrins by Staphylococcus aureus as well as the exploitation of IgCAMs by pathogenic Neisseria species.

Divergence and transcriptional analysis of the division cell wall (dcw) gene cluster in Neisseria spp.

Three of the 18 open reading frames in the division and cell wall synthesis cluster of the pathogenic Neisseria spp. are not present in the clusters of other bacterial species. The region containing two of these, dcaB and dcaC, displays interstrain and interspecies variability uncharacteristic of such clusters. 3' of dcaB is a Correia repeat enclosed element (CREE), which is only present in some strains. It has been suggested that this CREE is a transcriptional terminator, although we demonstrate otherwise. A gearbox-like promoter within this CREE is active in Escherichia coli but not in Neisseria meningitidis. There is an active promoter 5' of dcaC, although its sequence is not conserved. The presence of similarly located promoters has not been demonstrated in other species. In Neisseria lactamica, this promoter involves another dcw-associated CREE, the first demonstration of active promoter generation at the 5' end of this common intergenic, apparently mobile, element. Upstream of this promoter is an inverted pair of neisserial uptake signal sequences, which are commonly considered to be transcriptional terminators. It has been proposed to terminate transcription in this location, although we have demonstrated transcript extending through this uptake signal sequence. dcaC contains a 108 bp tandem repeat, which is present in different copy numbers in the neisserial strains examined. This investigation reveals extensive sequence variation, disputes the presence of transcriptional terminators and identifies active internal promoters in this normally highly conserved cluster of essential genes, and addresses the transcriptional activity of two common neisserial intergenic components.

M-6 endocarditis: report of an Australian case.

Neisseria elongata subsp. nitroreducens (formerly CDC group M-6) is a newly-recognized cause of particularly destructive endocarditis, frequently requiring valve replacement. We describe an Australian case of endocarditis caused by this organism, summarizing the clinical and microbiological features of this rarely isolated subspecies.

Neisseria ovis em ovinos / Neisseria ovis in sheeps

Säo relatados casos de ceratoconjuntivite provocados por Neisseria ovis em rebanho ovino das raças Merino, Ile de France, Ideal, Corriedale e Romny March. Os autores, após identificarem os microrganismo, selecionaram amostras que foram utilizadas para o preparo de vacina. Levando em consideraçäo as provas de patogenicidade experimental, variaçöes biológicas do parasito e fatores que predispöem o globo ocular à infecçäo, concluíram que o microrganismo apresenta capacidade para se instalar e proliferar em terreno previamente sensibilizado, desencadeando o processo oftálmico

Factors affecting the survival of Neisseria sicca.

Cultures of Neisseria sicca incubated at 37 degrees C died rapidly (within 36 h) after growth ceased. Re-suspending cells in a brain heart infusion broth and storing at 4 degrees C greatly reduced the rate of decline in viability (decimal reduction time 6 days). An important factor in maintaining viability was apparently the presence of external energy source(s). Survival comparable to that in broth was obtained by incubation in Ringer's solution with pyruvate plus glucose (but not with pyruvate or glucose alone). Medium pH had little effect on survival in the range pH 7.0 to 8.5. Energy sources also promoted survival of cells in Ringer's solution or a buffered salts solution at 37 degrees C. Highest levels of survival (up to 30% at 24 h) were obtained with pyruvate, lactate, proline and glutamate. A number of other amino acids and the tricarboxylic acid cycle intermediates, isocitrate, oxoglutarate, succinate, fumarate, malate and oxaloacetate, enhanced survival to a lesser extent.

Neisseria in early stage of dental plaque.

Neisseria in the early stage of dental plaque was studied. Two hundred seventeen strains of Neisseria were isolated from the 12-hour plaque of 9 subjects by using lactose-agar. The isolated strains were divided into 6 major groups with biological characteristics. One hundred twenty-one strains (56%) produced glycogen-like polysaccharide from sucrose. They were divided into 3 groups. Groups 1 and 2 were identified as N. mucosa and N. sicca, respectively. There were 106 strains of N. sica, being the most predominant of the species. The number of strains not producing polysaccharide was 96 (44%). Groups 4 and 5 were Branhamella and N. subflava. The absorption spectra of the ethanol extracts of the pigment in each group were similar and this result supported propriety of the classification by biological characteristics. The adhesiveness of Neisseria to the glass plate was examined. Approximately one-half of N. sica showed an adhesion capacity.

Effect of sonic treatment on pure cultures and aggregates of bacteria.

Pure cultures of a variety of bacteria were treated with ultrasonic energy using a sonic probe. Fractions of organisms killed at different sonic energies were calculated, and Streptococcus mutans was 600 times more resistant than Fusobacterium nucleatum, the most sensitive organism tested. The effects of sonic treatment on aggregates of bacteria were examined, and the results were interpreted as a model of the events that probably occur during the sonic dispersion of dental plaque.