Alcanivorax

Figure 1. Alcanivorax borkumensis. Image from Helmholtz Centre for Infection Research[1]

Classification

Bacteria; Phylum: Proteobacteria; Class: Gammaproteobacteria; Order: Oceanospirillales; Family: Alcanivoracaceae

Species

NCBI: Taxonomy

Alcanivorax balearicum
Alcanivorax borkumensis
Alcanivorax dieselolei
Alcanivorax indicus
Alcanivorax jadensis
Alcanivorax venustensis

Description and Significance

Figure 2. Supertanker Exxon Valdez grounded on Bligh Reef which released 11 million gallons of crude oil into the water. This oil-contaminated seawater is the preferred habitat for Alcanivorax. Image from USGS[2]

Alcanivorax, first described in 1998, is a Gram-negative, aerobic, rod-shaped, oil-degrading marine bacterium that is found in low abundances in unpolluted environments, but quickly becomes the predominant microbes in oil-contaminated open oceans and coastal waters when nitrogen and phosphorus are not limiting. When conditions in these moderately halophilic environments are right, Alcanivorax may make up 80-90% of the oil-degrading microbial community. As a result of their profound ability to degrade and live predominately on alkanes, as well as to become the dominant microbes in oil-contaminated areas, Alcanivorax plays a huge role in the biological cleanup of oil-contaminated environments. These oil-contaminated environments in the ocean are largely due to anthropogenic sources such as oil spills caused by tankers accidents, and cause serious ecological damage to coastal fauna and flora as well as other inhabitants of the ocean. Microbes such as Alcanivorax provide a major route for the breakdown of these pollutants, and demonstrate how marine bacteria keep the environment in check. Of all the Alcanivorax species and other oil-degrading microbes, Alcanivorax borkumensis is one of the most important worldwide due to the fact it produces a wide variety of very efficient oil-degrading enzymes. With this knowledge, Alcanivorax borkumensis could provide a useful tool for bioremediation of oil spills.

Genome Structure

The Alkanivorax Borkumensis strain SK2 was the first hydrocarbonoclastic bacterium to be sequenced and was completed by Susanne Schneiker et al. It's genome consists of a single circular chromosome with 3,120,143 base pairs with an average G+C content of 54.7%. The genomic analysis of A. Borkumensis SK2 revealed several new insights into the bacterium's role for (i) n-alkane degradation (which includes metabolism, biosurfactant production and biofilm production), (ii) it's system for capturing small amounts of nitrogen, phosphorous, sulfur, and other elements in a nutrient-poor marine environment, (iii) as well as means for coping with stress factors such as high salt contents and high UV radiation. It's genome encodes several systems for the catabolism of hydrocarbons which allow the bacertium to degrade all sorts of alkanes such as AlkB1 alkane hydroxylase which oxidizes medium-chain alkanes in the range of C5-C12, and AlkB2 alkane hydroxylase which oxidizes medium-chain alkanes in the range of C8 to C16. Both these systems are located close to the origin of replication of the chromosome.

Cell Structure, Metabolism and Life Cycle

Interesting features of cell structure; how it gains energy; what important molecules it produces.

Ecology and Pathogenesis

Habitat; symbiosis; biogeochemical significance; contributions to environment.
If relevant, how does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.