Analysis of the Pseudoalteromonas tunicata genome reveals properties of a surface-associated life style in the marine environment.
BACKGROUND
Colonisation of sessile eukaryotic host surfaces (e.g. invertebrates and seaweeds) by bacteria is common in the marine environment and is expected to create significant inter-species competition and other interactions. The bacterium Pseudoalteromonas tunicata is a successful competitor on marine surfaces owing primarily to its ability to produce a number of inhibitory molecules. As such P. tunicata has become a model organism for the studies into processes of surface colonisation and eukaryotic host-bacteria interactions.


RESULTS
To gain a broader understanding into the adaptation to a surface-associated life-style, we have sequenced and analysed the genome of P. tunicata and compared it to the genomes of closely related strains. We found that the P. tunicata genome contains several genes and gene clusters that are involved in the production of inhibitory compounds against surface competitors and secondary colonisers. Features of P. tunicata's oxidative stress response, iron scavenging and nutrient acquisition show that the organism is well adapted to high-density communities on surfaces. Variation of the P. tunicata genome is suggested by several landmarks of genetic rearrangements and mobile genetic elements (e.g. transposons, CRISPRs, phage). Surface attachment is likely to be mediated by curli, novel pili, a number of extracellular polymers and potentially other unexpected cell surface proteins. The P. tunicata genome also shows a utilisation pattern of extracellular polymers that would avoid a degradation of its recognised hosts, while potentially causing detrimental effects on other host types. In addition, the prevalence of recognised virulence genes suggests that P. tunicata has the potential for pathogenic interactions.


CONCLUSIONS
The genome analysis has revealed several physiological features that would provide P. tunciata with competitive advantage against other members of the surface-associated community. We have also identified properties that could mediate interactions with surfaces other than its currently recognised hosts. This together with the detection of known virulence genes leads to the hypothesis that P. tunicata maintains a carefully regulated balance between beneficial and detrimental interactions with a range of host surfaces.
Thomas
Torsten
T
Centre of Marine Bio-Innovation and School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales, Australia. t.thomas@unsw.edu.au
Evans
Flavia F
FF
Schleheck
David
D
Mai-Prochnow
Anne
A
Burke
Catherine
C
Penesyan
Anahit
A
Dalisay
Doralyn S
DS
Stelzer-Braid
Sacha
S
Saunders
Neil
N
Johnson
Justin
J
Ferriera
Steve
S
Kjelleberg
Staffan
S
Egan
Suhelen
S
D020591:Alteromonas / Q000235:genetics; D018441:Biofilms; D010861:Fimbriae, Bacterial / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D016678:Genome; D016680:Genome, Bacterial; D008957:Models, Genetic; D005810:Multigene Family; D010802:Phylogeny; D011108:Polymers / Q000737:chemistry; D031161:Pseudoalteromonas / Q000235:genetics* / Q000502:physiology*; D017422:Sequence Analysis, DNA; D013499:Surface Properties; D014774:Virulence / Q000235:genetics; D014871:Water Microbiology
D011108:Polymers