ABSTRACT: In order to expand upon the discovery that specific proteins survive in seawater as dissolved protein and that the origin of these proteins is bacterial porin, we surveyed marine environments and cultured bacteria for the presence of homologues of 2 kinds of bacterial porins. Antisera against the N-terminus of the OprP porin of Pseudomonas aeruginosa and against the whole molecule of the Omp35La porin of Listonella (Vibrio) anguillarum were prepared and used as probes in Western blot analysis. In all samples collected in the subarctic and subtropical Pacific Ocean and the Antarctic Ocean, proteins reactive to the antisera were detected. The molecular masses of OprP and Omp35La are 48 and 33 to 37 kDa respectively; detected proteins in seawater samples were generally also of similar molecular mass. However, dissolved proteins as well as outer membrane proteins from cultured bacteria with different molecular masses were detected using the antisera. This indicates that dissolved proteins and bacterial outer membrane proteins distinct from OprP and Omp35La contain similar antigenic structures to OprP and Omp35La. Fluorescent-antibody staining revealed that bacterial cells that were stainable with antisera were present in natural bacterial assemblages throughout the entire water column. Present observations strongly suggest that bacterial porins are a major source of dissolved proteins.

KEY WORDS: Dissolved protein · Bacteria · Porin

Published in MEPS Vol. 158 (1997) on November 17
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1997