Biomedical subjects

E R Angert

Publications and source records attributed to E R Angert.

5 recordsLinked to original sources

PubMed1999

Septal localization of penicillin-binding protein 1 in Bacillus subtilis.

Previous studies have shown that Bacillus subtilis cells lacking penicillin-binding protein 1 (PBP1), encoded by ponA, have a reduced growth rate in a variety of growth media and are longer, thinner, and more bent than wild-type cells. It was also recently shown that cells lacking PBP1 require increased levels of divalent cations for growth and are either unable to grow or grow as filaments in media low in Mg2+, suggesting a possible involvement of PBP1 in septum formation under these conditions. Using epitope-tagging and immunofluorescence microscopy, we have now shown that PBP1 is localized at division sites in vegetative cells of B. subtilis. In addition, we have used fluorescence and electron microscopy to show that growing ponA mutant cells display a significant septation defect, and finally by immunofluorescence microscopy we have found that while FtsZ localizes normally in most ponA mutant cells, a significant proportion of ponA mutant cells display FtsZ rings with aberrant structure or improper localization, suggesting that lack of PBP1 affects FtsZ ring stability or assembly. These results provide strong evidence that PBP1 is localized to and has an important function in the division septum in B. subtilis. This is the first example of a high-molecular-weight class A PBP that is localized to the bacterial division septum.

Bacillus subtilis↗

PubMed1998

Propagation by sporulation in the guinea pig symbiont Metabacterium polyspora.

The Gram-positive bacterium Metabacterium polyspora is an uncultivated symbiont of the guinea pig gastrointestinal tract. Here we present evidence that in M. polyspora vegetative cell division has taken on a minor, and apparently dispensable, role in propagation. Instead, this unusual bacterium has evolved the capacity to produce progeny in the form of multiple endospores. Endospore formation is coordinated with transit of the bacterium through the gastrointestinal tract of the guinea pig. For the majority of cells, sporulation is initiated in the ileum, whereas later stages of development take place in the cecum. We show that multiple endospores are generated both by asymmetric division at both poles of the cell and by symmetric division of the endospores at an early stage of their development. Our findings suggest that M. polyspora represents an intermediate step in the evolution of a novel mode of cellular propagation that originates with endospore-forming Bacillus and Clostridium spp., which reproduce by binary fission, and extends to Epulopiscium spp., which create multiple viviparous offspring by a process of internal reproduction.

Animals↗

PubMed1997

Assembly of the cell division protein FtsZ into ladder-like structures in the aerial hyphae of Streptomyces coelicolor.

In the filamentous bacterium Streptomyces coelicolor, the cell division protein FtsZ is required for the conversion of multinucleoidal aerial hyphae into chains of uninucleoidal spores, although it is not essential for viability. Using immunofluorescence microscopy, we have shown that FtsZ assembles into long, regularly spaced, ladder-like arrays in developing aerial hyphae, with an average spacing of about 1.3 microm. Within individual hyphae, ladder formation was relatively synchronous and extended for distances over 100 microm. These ladders were present only transiently, decreasing in intensity as chromosomes separated into distinct nucleoids and disappearing upon the completion of septum formation. Evidence from the overall intensity of immunofluorescence staining suggested that ladder formation was regulated in part at the level of the accumulation and degradation of FtsZ within individual aerial hyphae. Finally, FtsZ ladder formation was under developmental control in that long arrays of FtsZ rings could not be detected in certain so-called white mutants (whiG, whiH and whiB), which are blocked in spore formation. The assembly of FtsZ into ladders represents the earliest known molecular manifestation of the process of spore formation, and its discovery provides insight into the role of whi genes in the conversion of aerial hyphae into chains of spores. We have also described a novel use of a cell wall-staining technique to visualize apical tip growth in vegetatively growing hyphae.

Antibodies, Bacterial↗

PubMed1996

Phylogenetic analysis of Metabacterium polyspora: clues to the evolutionary origin of daughter cell production in Epulopiscium species, the largest bacteria.

It is rare that there are molecular clues to the evolutionary origin of developmental traits. We have encountered an evolutionary juxtaposition that may explain the origin of the unique replicative morphology of Epulopiscium spp., the largest known bacteria, which reproduce by the internal production of multiple live offspring. We report here a 16S rRNA-based phylogenetic analysis of Metabacterium polyspora, a multiple-endospore-forming, uncultivated inhabitant of guinea pig cecum. Cells of M. polyspora were harvested from cecum contents by sedimentation in a Ficoll gradient and lysed. The bacterial 16S rRNA genes of this lysate were amplified by PCR. Sequence analysis of the cloned PCR products revealed two dominant, closely related 16S rRNA types. In situ hybridization of cecum contents with fluorescently labeled oligonucleotides, diagnostic of these two sequences, showed that they represent distinct strains of M. polyspora. Phylogenetic analyses of the sequences showed that M. polyspora is closely related to Epulopiscium spp. On the basis of this result and other correlations, we propose that the process of sporulation was modified in a predecessor of Epulopiscium spp. to produce live offspring instead of quiescent endospores.

Animals↗

PubMed1993

The largest bacterium.

The large, morphologically peculiar microorganism Epulopiscium fishelsoni inhabits the intestinal tract of Acanthurus nigrofuscus, a brown surgeonfish (family Acanthuridae) from the Red Sea. Similar microorganisms have been found in surgeonfish species from the Great Barrier Reef. As these microorganisms have only been seen in surgeonfish and no free-living forms have been found, they are considered to be specific symbionts of surgeonfish, although the nature of the symbiosis is unclear. Initial reports considered them to be eukaryotic protists, based primarily on their size, with individuals being larger than 600 microns by 80 microns. But their cellular morphology in the electron microscope is more like that of bacterial than eukaryotic cells. To resolve the nature of these symbionts, we have isolated the genes encoding the small subunit ribosomal RNA from two morphotypes and used them in a phylogenetic analysis. In situ hybridization with oligonucleotide probes based on the cloned rRNA sequences confirmed the source of the rRNA genes. Our result identify the symbionts as members of the low-(G+C) Gram-positive group of bacteria. They are therefore the largest bacteria to be described so far.

Animals↗