Presence of thermophilic bacteria in laundry and domestic hot-water heaters

Thermophilic bacteria resembling Thermus aquaticus were isolated from hot water taken from domestic and commercial hot-water tanks. Cold water from the same locations never yielded thermophilic bacteria, suggesting that the bacteria were growing in the tanks. In contrast to the T. aquaticus isolates from hot springs, the present isolates were rarely pigmented. In general, the hotter sources more frequently yielded bacteria.