Green Nonsulfur Bacteria

Abstract

Formerly known only as a group of gliding filamentous bacteria capable of anoxygenic photosynthesis, the green nonsulfur bacteria (phylum Chloroflexi) now are also known to comprise numerous chemotrophic bacteria of diverse ecophysiology and phylogeny. The most conspicuous representatives are the green- or orange-coloured thermophilic bacteria which form dense microbial mats in hot springs. They are typical photoorganoheterotrophs and well adapted to their changing environment by their gliding motility, tactic responses and versatile physiology. Culture-independent studies have revealed a plethora of novel, unknown 16S ribosomal ribonucleic acid (rRNA) gene sequence types, indicating that the diversity of these bacteria in the natural environment is only marginally understood. Nonphotosynthetic members of the Chloroflexi occur in freshwater, soil and decaying organic matter, as well as methanogenic granular sludge and other wastewater treatment systems where they seem to aid in granule formation and participate in carbohydrate turnover.