IMMUNOFLUORESCENCE DETECTION OF THE DENITRIFYING STRAIN PSEUDOMONAS-STUTZERI (ATCC-14405) IN SEAWATER AND INTERTIDAL SEDIMENT ENVIRONMENTS

A strain-specific immunofluorescence assay for enumeration of a marine denitrifying bacterium was developed and applied in the marine enviro nment. The polyclonal antiserum for Pseudomonas stutzeri (ATCC 14405) did not react with other pseudomonads, other heterotrophs, or autotrop hic nitrifying strains. The abundance of P. stutzeri in the shallow wa ter column of Monterey Bay was less than 0.1% of the total bacterial a bundance and decreased with depth, whereas the total bacterial abundan ce was variable and nearly constant with depth. P. stutzeri was also d etected in the sediments of a microbial mat from Tomales Bay. The rela tively low contribution of P. stutzeri to the total bacterial abundanc e in both environments implies that it is not a major component of the heterotrophic assemblage. This conclusion appears to hold for most ot her strains for which specific assays have been applied in the marine environment. The isolation of several different denitrifying strains f rom local marine environments implies that the culturable population i s quite diverse, even in the absence of different selective enrichment media. Thus, strain specific immunofluorescence is of limited use in quantifying functional groups of bacteria. Conversely, they provide sp ecific information on the diversity of natural populations and their r elation to culturable strains.