MICROBIOLOGY

Mud samples were collected from Holes 1269A and 1269C for microbial analysis. Samples were taken from sediment recovered from the core barrel after a push-in test with the drill bit to determine sediment thickness. Microscopic observation showed that the samples were composed of nannofossils and fine inorganic particulates. Because no mudline was established, no sample designation was assigned beyond hole number. From Holes 1269A and 1269C, 9.0 and 18.3 g of reddish brown mud were collected, respectively. Direct counts and culture of the samples were prepared as described in "Microbiology" in the "Explanatory Notes" chapter and Table T2. As no bacteria were observed in the Hole 1269A sample, 10 µL of the cleared artificial seawater was used to prepare a dilution series to 10–7, and 100 µL of each dilution spread was plated onto nutrient agar and incubated at room temperature. No growth was observed on any of the plates after 72 hr of incubation. When no growth was noted at 24 hr of incubation, both samples (from Holes 1269A and 1269C) were again mixed by shaking until the mud sediments were in solution. Ten microliters from each sample (no clearing allowed) was added to 900 µL of artificial seawater and spread over a 45-mm nitrocellulose membrane filter that had been placed on nutrient agar plates. Excess water was aspirated off the filters with a pipette, leaving the sediment particles on the filter surface. Growth was noted on both plates at 24 hr, indicating that the bacteria in the samples were predominantly associated with sediments.

NEXT