Insights into the planktonic to sessile transition in a marine biofilm-forming Pseudoalteromonas isolate using comparative proteomic analysis

Abstract

Bacterial biofilms play an important role in marine biofouling. The formation of a biofilm starts when marine bacterial cells transition from a planktonic to an attached state. However, the molecular mechanisms involved in this transition are poorly understood. Here, 51 strains of marine bacteria were isolated from natural biofilms growing on submerged artificial surfaces (glass slides, epoxy panels, and bridge pillars) and evaluated for their biofilm-forming capacity. Eleven strains formed relatively strong biofilms and 16S rRNA gene sequence analysis indicated that they belonged to the genera Leisingera, Roseobacter, Pseudoalteromonas, Alteromonas, Tenacibaculum, Vibrio, Chryseobacterium, Aquimarina, and Acinetobacter. Strain Pseudoalteromonas sp. W-7 showed efficient and rapid attachment and was therefore chosen for further study. An iTRAQ-based comparative proteomic analysis of planktonic and attached strain W-7 cells was carried out. A total of 3468 proteins were identified, of which 163 showed significant differential expression (120 down-regulated and 43 up-regulated in attached cells relative to planktonic cells). KEGG (Kyoto encyclopedia of genes and genomes) analysis indicated that pyruvate metabolism, carbon fixation, and carbon metabolism were significantly affected in attached cells. Up-regulated proteins such as UTP-glucose-1-phosphate uridylyltransferase, acetyltransferase component of pyruvate dehydrogenase complex, OmpA-like protein, and acetyl-coenzyme A synthetase may be important during initial adhesion. Our findings provide a deeper understanding of the planktonic to sessile transition of marine fouling bacteria.