Caloramator indicus sp. nov., a New Thermophilic Anaerobic Bacterium Isolated from the Deep-Seated Nonvolcanically Heated Waters of an Indian Artesian Aquifer

Abstract

A new thermophilic, glucose-fermenting, anaerobic isolate, strain IndiB4T, was obtained from the nonvolcanically heated waters of an Indian artesian basin bore and was named Caloramator indicus. The cells of this organism were rod shaped to filamentous and occurred singly, in pairs, or in short chains. Motility and spores were not observed. Electron micrographs of thin sections revealed a typical gram-positive cell wall structure, although the cells stained gram negative. The optimum temperature for growth was 60 to 65°C, the maximum temperature was 75°C, and the minimum temperature was more than 37°C. Growth occurred at pH values between 6.2 and 9.2, and the optimum pH was between 7.5 and 8.1. The generation time of C. indicus at the optimal temperature and optimal pH was 20 min. The DNA base composition was 25.6 ± 0.3 mol% guanine plus cytosine as determined by thermal denaturation. Strain IndiB4T utilized a wide range of carbohydrates, including starch, amylopectin, sucrose, mannose, lactose, fructose, and cellobiose. Ethanol, acetate, lactate, CO2, and H2 were the end products of glucose fermentation. Growth was inhibited by pencillin, tetracycline, and chloramphenicol, indicating that the organism is a member of the domain Bacteria. A phylogenetic analysis of the 16S rRNA gene revealed that strain IndiB4T is affiliated with the low-guanine-plus-cytosine-content subgroup of the gram-positive phylum. The type strain of C. indicus is strain IndiB4 (= ACM 3982).