Among the nitrogen-fixing bacteria associated with roots of (L.) Kunth in saline-sodic soils in the Punjab of Pakistan, we repeatedly found yellow-pigmented, straight to curved, gram-negative rods. To group and identify these organisms, we examined morphological, nutritional, and biochemical features and performed polyacrylamide gel electrophoretic analyses of cellular proteins, gas chromatographic analyses of fatty acids, DNA-rRNA hybridizations, and DNA-DNA hybridizations. Our results showed that 11 isolates formed five groups distinct at the species level, with each group containing one to three members. These bacteria constituted a separate rRNA branch in rRNA superfamily III (corresponding to the beta subclass of the ) at a branching level of 67.7°C [ is the temperature at which 50% of a hybrid is denatured under standard conditions]. On this branch, the five groups were located in two clusters with values of 79.4 to 80.4°C and around 71.5°C. We propose a new genus, the genus , for these strains. is the type species and has a growth factor requirement; its type strain is strain VB32 (= LMG 9092). A second named species, , includes a strain obtained from French refinery oily sludge, strain LMG 5514. Bacteria of this genus have a strictly aerobic type of metabolism, fix nitrogen microaerobically, and grow well on salts of organic acids but not on carbohydrates. Swedish isolates obtained from human sources (E. Falsen group 15 strains LMG 6115 and LMG 6116), as well as “[ LMG 7583, were also located on this rRNA branch at a lower level (70.4 to 71.2°C).


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