Dichotomicrobium thermohalophilum, gen. nov., spec, nov., Budding Prosthecate Bacteria from the Solar Lake (Sinai) and Some Related Strains

Abstract

Summary Ten strains of budding bacteria with dichotomously branching hyphae have been isolated from various depths of the Solar Lake (Sinai, near Elat). Three additional strains of similar bacteria came from a shallow coastal saline lake in Brazil. All of these 13 strains had a similar morphology: nearly tetrahedral mother cells produced up to 4 hyphae at the tips of which non-motile buds were formed. Dichotomous branching of the hyphae often resulted in the formation of chains or even nets. Contrary to all other budding, hyphal bacteria, these isolates contained poly-β-hydroxybutyrate granules in their hyphae. Liquid cultures showed reddish pigmentation (carotenoids), and colonies on solid media were dark brown with fuzzy edges. The organisms stained Gram-negative. All strains required yeast extract for growth, and all strains were moderately thermophilic and halotolerant. The maximum temperature tolerated for growth was between 52 and 65°C. The 13 strains were strictly aerobic, heterotrophic, and they utilized a few organic acids, notably those of the tricarboxylic acid cycle (malate, succinate). Growth with sugars was poor and variable. A few amino acids were utilized for growth. Inorganic nitrogen sources did not support growth, but amino acids, especially glutamate, arginin, leucin, methionin and cystein were utilized by some strains. Excellent growth occurred on sheep blood agar, but there was no hemolysis. Growth was significantly inhibited by 1–10 μg/ml of penicillin G and some other antibiotics. All 13 of these strains were sufficiently alike to include them in a new genus, and the ten strains from the Solar Lake are considered to represent one species. The genus name, Dichotomicrobium gen. nov. is proposed, with the type species, D. thermohalophilum n. sp. The type strain, IFAM 954, had 64 mol% G+C and it has been deposited in the Deutsche Kultursammlung fur Mikroorganismen (DSM 5002).