A Microbial Biorealm page on the Prosthecobacter
Higher order taxa:
Bacteria; Chlamydiae/Verrucomicrobia group; Verrucomicrobia; Verrucomicrobiae; Verrucomicrobiales; Verrucomicrobiaceae
Prosthecobacter debontii, P. dejongeii, P. fusiformis
Description and Significance
Prosthecobacter were originally described as fusiform caulobacter. They are Gram-negative, obligate aerobic bacteria. Although usually independent organisms, sometimes individual Prosthecobacter will aggregate.
A distinctive characteristic of Prosthecobacter is the presence of tubulin-like genes. Tubulins, which are compoents of the microtubule cytoskeleten, have never been observed in bacteria. Most bacteria have a homologous structure, FtsZ. Prosthecobacter are the exception to this, containing genes that have higher sequence-homology to eukaryotic tubulin than FtsZ. These genes are called bacterial tubulin a (BtubA) and bacterial tubulin b (BtubB). The properties are not exactly same. For example, dimerization is weak and chaperone folding is independent. However, surface loops and protofilaments are extremely similar. It has been hypothesized that BtubA and BtubB were transferred to Prosthecobacter from eukaryotic cells through horizontal gene transfer.
Cell Structure and Metabolism
A distinguishing factor of Prosthecobacter is the presence of prosthecae. Prosthecae are narrow extensions of the cell wall. They contain cytoplasm. Prosthecobacter have a single polar prosthecae. Prosthecobacter have cell walls made out of peptidoglycan. These cells are coccoid, rod, or fusiform-shaped and nonmotile.
Prosthecobacter are heterotrophic organisms. They are often refereed to as oligotrophic bacteria, meaning that they thrive in low-nutrient environments. In fact, diluted nutrients are required for growth.
Prosthecobacter fusiformis lacks a dimorphic life cycle. Instead, members of this organism divide symmetrically. The new cells that result have prostheca at the time of division.
Prosthecobacter are freshwater organisms. They have also been reported in antarctic sea ice.
Hedlund, Brian P., John J. Gosink, and James T. Staley. "Phylogeny of Prosthecobacter, the Fusiform Caulobacters: Members of a Recently Discovered Division of the Bacteria." International Journal of Systematic Bacteriology. October 1996;46(4):960-966.
Jenkins, Cheryl, Ram Samudrala, Iain Anderson, Brian P. Hedlund, Giulio Petroni, Natasha Michailova, Nicoals Pinel, Ross Overbeek, Giovanna Rosati, and James T. Staley. "Genes for the cytoskeletal protein tubulin in the bacterial genus Prosthecobacter." PNAS. December 2004;99(26):1704917054.