ABSTRACT
A strain of aerobic anoxygenic phototrophic bacteria (AAPB) isolated from the surface of a cyano- bacterial mat of an Eastern Siberian thermal spring (40 C) and designated Se 4 was identified as Porphyro- bacter donghaensis according to its 16S rRNA gene sequence. A DNA-DNA hybridization level of 95% was determined between strain Se-4 and the type strain of this species; SW-132@T. The isolate was an obligate aerobe,. forming orange round colonies on solid media, which turn red in the course of growth. The cells were motile rods capable of branching. The cells divided by uniform fission by constriction. Optimal growth was observed at pH 7.5 and NaCl concentrations from 0 to 1 g/L. The pigments present were carotenoids and bacteriochlorophyll a. Another Porphyrobacter donghaensis strain, Noj- 1, isolated from a purple mat developing on the surface of a coastal set-up in a steppe low-mineralization (1.5 g/L) soda lake Nozhii (Eastern Siberia) possessed similar characteristics. Thus, the AAPB species Porphyrobacter donghaensis was shown to-occur, apart from its known habitat, marine environments, in low-mineralization soda lakes and freshwater thermal springs. Description of the species Porphyrobacter donghaensis was amended.
