Bacteriology of ferromanganese nodules from the Indian Ocean

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Abstract
Bacteriological investigations of the ferromanganese nodules collected from the Indian Ocean indicate that the microbial populations associated with the nodules are, in general, comparable to those of the Pacific and Atlantic Oceans. Both Mn(II)‐oxidizing and MnO2‐reducing psychrotrophic bacteria were present in the nodules. The maximum percentage of oxidizers was noticed on the surface of the nodules. The sediments harbored more inactive forms. Members of Vibrio, Enterobacteriaceae, Bacillus, Micrococcus, Sta‐phylococcus, Arthrobacter, and coryneforms were encountered in the present study. Most of the isolates were able to grow on a wide range of sodium chloride concentrations (0 to 10%). The isolates elaborated a number of hydrolytic enzymes, namely, amylase, gelatinase, lipase, and phosphatase. The dominance of the gram‐positive group is attributed to terrigenous influences. The present study clearly indicates that Indian Ocean nodules also harbor a variety of heterotrophic bacteria capable of mobilizing and immobilizing manganese.