Nitrogen-Fixing Bacteria from Warty Lenticellate Bark of a Mangrove Tree, Bruguiera gymnorrhiza (L.) Lamk

Abstract

Detached warty lenticellate bark of a mangrove tree species, Bruguiera gymnorrhiza (L.) Lamk. from Iriomote Island, Okinawa, a subtropical region of Japan, showed development of acetylene reduction activity when incubated in a mineral nutrient solution lacking nitrogen under an atmosphere consisting of 5% O₂, 90% N₂, and 5% C₂H₂. The bacteria responsible for nitrogen fixation were isolated from the bark, and their capacity for acetylene reduction and the incorporation of ¹⁵N₂ into the bacterial cells was confirmed. Four representative strains of the isolates were subjected to taxonomic classification. Two strains were similar to Enterobacter cloacae, and another resembled Enterobacter aerogenes. The characteristics of the fourth strain were similar to those of Klebsiella planticola (Bagley et al., Curr. Microbiol. 6:105-109, 1981). The results of this investigation suggest that the acetylene reduction activity of lenticellate warts of mangrove trunk bark is due to the presence in the warts of nitrogen-fixing bacteria belonging to the family Enterobacteriaceae.