Sporulation and Germination

Doi, Roy H.

doi:10.1007/978-1-4899-3502-1_8

Cited by 27 publications

(14 citation statements)

References 221 publications

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“…In Myxococcus spp. and Bacillus subtilis, autocideinduced killing events occur as part of an adaptive program culminating in sporulation (16,50,67,68). This study demonstrated that cell death also occurs during P. aeruginosa biofilm differentiation and involves a genomic prophage.…”

Section: Resultsmentioning

confidence: 64%

Cell Death in Pseudomonas aeruginosa Biofilm Development

et al. 2003

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Bacteria growing in biofilms often develop multicellular, three-dimensional structures known as microcolonies. Complex differentiation within biofilms of Pseudomonas aeruginosa occurs, leading to the creation of voids inside microcolonies and to the dispersal of cells from within these voids. However, key developmental processes regulating these events are poorly understood. A normal component of multicellular development is cell death. Here we report that a repeatable pattern of cell death and lysis occurs in biofilms of P. aeruginosa during the normal course of development. Cell death occurred with temporal and spatial organization within biofilms, inside microcolonies, when the biofilms were allowed to develop in continuous-culture flow cells. A subpopulation of viable cells was always observed in these regions. During the onset of biofilm killing and during biofilm development thereafter, a bacteriophage capable of superinfecting and lysing the P. aeruginosa parent strain was detected in the fluid effluent from the biofilm. The bacteriophage implicated in biofilm killing was closely related to the filamentous phage Pf1 and existed as a prophage within the genome of P. aeruginosa. We propose that prophage-mediated cell death is an important mechanism of differentiation inside microcolonies that facilitates dispersal of a subpopulation of surviving cells.

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Section: Resultsmentioning

confidence: 64%

Cell Death in Pseudomonas aeruginosa Biofilm Development

et al. 2003

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“…The cortex is apparently responsible for the maintenance of spore dormancy (7). The last characteristic morphological event to occur during sporulation is the lysis of the mother cell, which allows release of the mature spore (5). At the onset of germination, the cortex is selectively hydrolyzed, leaving a thin layer of vegetative cell peptidoglycan which forms the basis of the new vegetative cell wall (4,10).…”

Section: Discussionmentioning

confidence: 99%

Analysis of the autolysins of Bacillus subtilis 168 during vegetative growth and differentiation by using renaturing polyacrylamide gel electrophoresis

1992

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The autolysins of Bacillus subtilis 168 were analyzed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis with substrate-containing gels. Four bands of vegetative autolytic activity of 90, 50, 34, and 30 kDa (bands Al to A4) were detected in SDS and LiCl extracts and in native cell walls by using B. subtilis 168 vegetative cell walls as the substrate incorporated in the gel. The four enzyme activities showed different substrate specificities and sensitivities to various chemical treatments. The autolysin proffle was not medium dependent and remained constant during vegetative growth. During sporulation, band A4 greatly increased in activity just prior to mother-cell lysis. No germination-associated changes in the profile were observed, although a soluble 41-kDa endospore-associated cortex-lytic enzyme was found. By using insertionally inactivated mutants, bands Al and A2 were positively identified as the previously characterized 90-kDa glucosaminidase and 50-kDa amidase, respectively. The common filamentous phenotype of various regulatory mutants could not be correlated to specific changes in the autolysin profile.Despite abundant speculation, the role of bacterial autolysins during cell growth and division has remained elusive. All bacteria apparently possess a complement of potentially lethal autolysins capable of hydrolyzing the cell wall peptidoglycan (13). Bacillus subtilis 168 has two major vegetative autolysins, a 50-kDa amidase and a 90-kDa glucosaminidase, which have been purified and characterized (17, 31). During sporulation, two distinct lytic enzymes, an amidase and an endopeptidase, have been identified but not studied in detail (14). A 30-kDa amidase has also been identified, and the gene has been cloned and studied at the molecular level (9, 22). The specific function of all of these enzymes is at present unknown, as is the total number of B. subtilis 168 autolytic enzymes. Work mainly using regulatory mutants with reduced autolysin levels (lyt) has implicated them in several important cellular functions, including cell wall turnover, cell separation, flagellation, competence, and the lytic action of penicillin (8,28,30). The regulatory mutants sigD and sin share a common filamentous and Lyt-phenotype, and the lack of cell separation has been proposed to be due to reduced expression of autolysin genes (12,16,25,32). In some lyt mutants, however, the rate of wall turnover was dependent on the salt concentration, and the mutants showed levels of wall turnover comparable to that of the wild type when they were grown in high salt concentrations (38). Because of the possible functional redundancy (9) and compensatory effect of multiple autolysins, it is important to identify and characterize the total set of such enzymes present during growth and development in order to be able to assess their involvement in any given cellular process.The ability of autolysins to renature after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) has allowed their activity to be studied ...

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“…Gram-positive bacteria typically have a cell wall consisting of a thick layer of peptidoglycan (19), while a few rather unusual genera lack a cell wall entirely (42). Many in this large group of primarily chemoorganotrophic bacteria are also known to produce spores in response to starvation or harsh chemical or physical conditions (17,40,50). Aerobic gram-positive bacteria, specifically actinomycetes (defined here as bacteria within the order Actinomycetales) and members of the order Bacillales, are generally saprophytic and include well-known producers of important secondary metabolites (23,53).…”

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confidence: 99%

Phylogenetic Diversity of Gram-Positive Bacteria Cultured from Marine Sediments

Gontang

Fenical

Jensen

2007

Appl Environ Microbiol

300

238

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Major advances in our understanding of marine bacterial diversity have been gained through studies of bacterioplankton, the vast majority of which appear to be gram negative. Less effort has been devoted to studies of bacteria inhabiting marine sediments, yet there is evidence to suggest that gram-positive bacteria comprise a relatively large proportion of these communities. To further expand our understanding of the aerobic gram-positive bacteria present in tropical marine sediments, a culture-dependent approach was applied to sediments collected in the Republic of Palau from the intertidal zone to depths of 500 m. This investigation resulted in the isolation of 1,624 diverse gram-positive bacteria spanning 22 families, including many that appear to represent new taxa. Phylogenetic analysis of 189 representative isolates, based on 16S rRNA gene sequence data, indicated that 124 (65.6%) belonged to the class Actinobacteria while the remaining 65 (34.4%) were members of the class Bacilli. Using a sequence identity value of >98%, the 189 isolates grouped into 78 operational taxonomic units, of which 29 (37.2%) are likely to represent new taxa. The high degree of phylogenetic novelty observed during this study highlights the fact that a great deal remains to be learned about the diversity of gram-positive bacteria in marine sediments.Gram-positive bacteria can be divided into two major subdivisions: the phylum Actinobacteria, also described as the high-GϩC gram-positives, and the phylum Firmicutes, also known as the low-GϩC gram-positives, a group that includes such well-known genera as Bacillus and Clostridium (21). Gram-positive bacteria typically have a cell wall consisting of a thick layer of peptidoglycan (19), while a few rather unusual genera lack a cell wall entirely (42). Many in this large group of primarily chemoorganotrophic bacteria are also known to produce spores in response to starvation or harsh chemical or physical conditions (17,40,50). Aerobic gram-positive bacteria, specifically actinomycetes (defined here as bacteria within the order Actinomycetales) and members of the order Bacillales, are generally saprophytic and include well-known producers of important secondary metabolites (23,53).While the most thoroughly studied gram-positive bacteria include human pathogens (e.g., Mycobacterium tuberculosis, Bacillus anthracis) and soil-derived, antibiotic-producing actinomycetes (2), relatively little is known about the diversity and distribution of gram-positive bacteria in the marine environment. This lack of information persists despite the fact that gram-positive bacteria have been cultured from the ocean for decades (5,26,32,43,68) and consistently appear in culture-independent studies (e.g., references 62 and 66), including the report of a new and as-yetuncultured order within the class Actinobacteria (54). Gram-positive bacteria are likely to play important microbiological roles in the marine environment, yet without a fundamental understanding of their diversity and ecophysiology, it is diffi...

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Sporulation and Germination

Cited by 27 publications

References 221 publications

Cell Death in Pseudomonas aeruginosa Biofilm Development

Cell Death in Pseudomonas aeruginosa Biofilm Development

Analysis of the autolysins of Bacillus subtilis 168 during vegetative growth and differentiation by using renaturing polyacrylamide gel electrophoresis

Phylogenetic Diversity of Gram-Positive Bacteria Cultured from Marine Sediments

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