Application of antisera raised against sulfate-reducing bacteria for indirect immunofluorescent detection of immunoreactive bacteria in sediment from the German Baltic Sea.

Polyclonal rabbit antisera raised against sulfate-reducing bacteria (SRB) could detect several distinct populations of bacteria in sediment from the German Baltic Sea. The depth distribution of immunoreactive bacteria was determined by an indirect immunofluorescence filter method. Anti-Desulfovibrio desulfuricans DSM 1926 serum showed maximum bacterial numbers at a depth of 18 cm, with a concentration of 60 x 10(6) cells cm-3. With anti-Desulfovibrio baculatus DSM 2555 serum, counts were highest at the same depth, approaching 0.7 x 10(6) cells cm-3. Other significantly smaller populations were observed. Anti-SRBStrain 1 (lactate,vibrio) maxima were at 0 to 4 cm and at 17 to 18 cm. Anti-SRBStrain 2 (lactate,vibrio) serum showed several local maxima. Anti-SRBStrain 3 (lactate,oval) serum detected one single peak at a depth of 10 to 12 cm. Also determined were rates of sulfate reduction, total bacterial counts by acridine orange staining, and the viable counts by dilution series on anaerobic lactate medium. The total bacterial counts were highest (180 x 10(6) cells cm-3) at 3 to 4 cm and dropped to 24 x 10(6) cells cm-3 at 10 to 11 cm but showed additional local maxima reaching 140 x 10(6) cells cm-3 at a depth of 17 to 18 cm. Viable counts probable number) were above 10(5) CFU cm-3 at 0 to 3.6 cm but remained below 10(3) CFU at 7.2 to 18 cm. The sulfate reduction rate was maximal (107 nmol cm-3 day-1) at a depth of 1 to 2 cm, dropped to 10 nmol cm-3 day-1 at 12 to 13 cm, and reached 38 nmol cm-3 day-1 at 17 to 18 cm.