Isolation and characterization of a novel hydrocarbon-degrading, Gram-positive bacterium, isolated from intertidal beach sediment, and description ofPlanococcus alkanoclasticus sp nov.

Aims: Characterization of a bacterial isolate (strain MAE2) from intertidal beach sediment capable of degrading linear and branched alkanes. Methods and Results: A Gram-positive, aerobic, heterotrophic bacterium (str ain MAE2), that was capable of extensive degradation of alkanes in crude oi l but had a limited capacity for the utilization of other organic compounds , was isolated from intertidal beach sediment. MAE2 had an obligate require ment for NaCl but could not tolerate high salt concentrations. It was capab le of degrading branched and n-alkanes in crude oil from C11 to C33, but wa s unable to degrade aromatic hydrocarbons. Comparative 16S rRNA sequence an alysis placed the isolate with members of the genus Planococcus. That findi ng was corroborated by chemotaxonomic and physiological data. The fatty aci d composition of strain MAE2 was very similar to the type species of the ge nus Planococcus, P. citreus (NCIMB 1493(T)) and P. kocurii (NCIMB 629(T)), and was dominated by branched acids, mainly a15:0. However, the 16S rRNA of strain MAE2 had less than 97% sequence identity with the type strains of P . citreus (NCIMB 1439(T)), P. kocurii (NCIMB 629(T)) and two Planococcus sp p. (strain MB6-16 and strain ICO24) isolated from Antarctic sea ice. This i ndicated that strain MAE2 represented a separate species from these planoco cci. Morphologically, the isolate resembled P. okeanokoites (NCIMB 561(T)) and P. mcmeekinii S23F2 (ATCC 700539(T)). The cellular fatty acid compositi on of P. okeanokoites and P. mcmeekinii was considerably different from str ain MAE2, and the mol % G + C content of P. mcmeekinii was far lower than t hat of MAE2. Conclusions: On the basis of phenotypic and genotypic data, it is proposed that strain MAE2 is a new species of Planococcus, Planococcus alkanoclastic us sp, nov., for which the type strain is P. alkanoclasticus MAE2 (NCIMB 13 489(T)). Significance and Impact of the Study: Planococcus species are abundant memb ers of the bacterial community in a variety of marine environments, includi ng some in sensitive Antarctic ecosystems. The occurrence of hydrocarbon-de grading Planococcus spp. is potentially of importance in controlling the im pact of hydrocarbon contamination in sensitive marine environments.