Gut of Higher Termites as a Niche for Alkaliphiles as Shown by Culture-Based and Culture-Independent Studies

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We screened alkaliphilic bacteria from the first proctodaeal region (P1) of the hindgut, which is known to show high alkalinity and K⁺ richness, of several species of higher termites. Phylogenetic analyses based on the 16S rDNA sequence revealed that most isolates were affiliated with known alkaliphilic bacilli, frequently isolated from soil. Though many physiological characteristics of the isolated strains were similar to those of soil alkaliphilic bacilli, some strains showed a distinctive NaCl sensitivity. Many strains grew better in an alkaline medium containing K₂CO₃ than one containing Na₂CO₃. One strain, closely related to the xylanolytic and alkaliphilic Paenibacillus sp. SM-XY60 from the soil-feeding termite Sinocapritermes mushae, was also isolated. Culture-independent analysis showed that bacteria closely related to our isolated alkaliphiles widely inhabit the termite gut. Our results also suggested that some alkaliphilic bacilli in soil share ecological niches in the termite gut.