Bacteria Genomes - PIRELLULA

Pirellula are part of a small but distinct group of heterotrophic bacteria called Planctomycetaceae. They are unique because of the stalk that they produce, which unlike that in Caulobacter is made of protein. The stalk is believed to be used as a means of attachment to substrates. They are primarily aquatic aerobic chemoorganotrophs.

They inhabit phytodetrital macroaggregates in marine environments and include one of the organisms known to derive energy from the anaerobic oxidation of ammonia. They catalyse important transformations in global carbon and nitrogen cycles. By their mineralisation of marine snow particles planctomycetes have a profound impact on global biogeochemistry and climate by affecting exchange processes between the geosphere and atmosphere.

The complete genome of Pirellula sp. strain 1 has been sequenced and a proteinaceous cell wall and remnants of genes for peptidoglycan synthesis were found. Genes for lipid A biosynthesis and homologues to the flagellar L- and P-ring protein indicate a former Gram-negative type of cell wall.

Pirellula gains energy from the aerobic oxidation of mono- or disaccharides derived from the cleavage of sulfated polymers produced by algae. Protection systems for UV protect Pirellula from irradiation at the water surface. Nitrate transporters support growth even under limited-nitrogen conditions common in continental shelf areas. Anoxic conditions force Pirellula to switch to heterolactic acid fermentation or pathways involving formaldehyde conversion if not to support growth, then at least to allow basic maintenance metabolism. With the expression of genes for carbon starvation Pirellula can even outlast periods of nutrient depletion. The formation of swarmer cells helps Pirellula to reach for new resources.

References:

Proc Natl Acad Sci U S A 2003, 100 (14):8298-303
http://blast.mpi-bremen.de/m_status_pirellula.php