Molecular evidence that the capacity for endosporulation is universal among phototrophic heliobacteria

Although enrichment cultures For anoxygenic phototrophic heliobacteria comm only contain sporulating cells, once strains of heliobacteria are obtained in pure culture, they all but cease to sporulate. In fact, some species of heliobacteria have never been observed to sporulate. Thus, despite their ph ylogenetic connection to endospore-forming bacteria, the question of sporul alion capacity in heliobacteria remains open. We have investigated this pro blem using PCR and Southern hybridization as tools and show here that all r ecognized species of heliobacteria tested, as well as several unclassified strains, contain homologs to the ssp genes of Clostridium and Bacillus spec ies, genes that encode key sporulation-specific proteins, It can therefore he concluded that as a group, heliobacteria are likely all to be endospore- forming bacteria in agreement with their phylogenetic placement within the 'low GC' Gram-positive bacteria. (C) 2001 Federation of European Microbiolo gical Societies. Published by Elsevier Science B.V. All rights reserved.