title: The genome of Heliobacterium modesticaldum, a phototrophic representative of the Firmicutes containing the simplest photosynthetic apparatus.
abstract: Despite the fact that heliobacteria are the only phototrophic representatives of the bacterial phylum Firmicutes, genomic analyses of these organisms have yet to be reported. Here we describe the complete sequence and analysis of the genome of Heliobacterium modesticaldum, a thermophilic species belonging to this unique group of phototrophs. The genome is a single 3.1-Mb circular chromosome containing 3,138 open reading frames. As suspected from physiological studies of heliobacteria that have failed to show photoautotrophic growth, genes encoding enzymes for known autotrophic pathways in other phototrophic organisms, including ribulose bisphosphate carboxylase (Calvin cycle), citrate lyase (reverse citric acid cycle), and malyl coenzyme A lyase (3-hydroxypropionate pathway), are not present in the H. modesticaldum genome. Thus, heliobacteria appear to be the only known anaerobic anoxygenic phototrophs that are not capable of autotrophy. Although for some cellular activities, such as nitrogen fixation, there is a full complement of genes in H. modesticaldum, other processes, including carbon metabolism and endosporulation, are more genetically streamlined than they are in most other low-G+C gram-positive bacteria. Moreover, several genes encoding photosynthetic functions in phototrophic purple bacteria are not present in the heliobacteria. In contrast to the nutritional flexibility of many anoxygenic phototrophs, the complete genome sequence of H. modesticaldum reveals an organism with a notable degree of metabolic specialization and genomic reduction.
authors.affiliation: Department of Biology, Washington University, Campus Box 1137, St. Louis, Missouri 63130, USA.
authors.forename: W Matthew
authors.initials: WM
authors.lastname: Sattley
authors.forename: Michael T
authors.initials: MT
authors.lastname: Madigan
authors.forename: Wesley D
authors.initials: WD
authors.lastname: Swingley
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Cheung
authors.forename: Kate M
authors.initials: KM
authors.lastname: Clocksin
authors.forename: Amber L
authors.initials: AL
authors.lastname: Conrad
authors.forename: Liza C
authors.initials: LC
authors.lastname: Dejesa
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Honchak
authors.forename: Deborah O
authors.initials: DO
authors.lastname: Jung
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Karbach
authors.forename: Ahmet
authors.initials: A
authors.lastname: Kurdoglu
authors.forename: Surobhi
authors.initials: S
authors.lastname: Lahiri
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Mastrian
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Page
authors.forename: Heather L
authors.initials: HL
authors.lastname: Taylor
authors.forename: Zi T
authors.initials: ZT
authors.lastname: Wang
authors.forename: Jason
authors.initials: J
authors.lastname: Raymond
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.forename: Robert E
authors.initials: RE
authors.lastname: Blankenship
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Touchman
mesh_terms: D000693:Anaerobiosis / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D016680:Genome, Bacterial; D006094:Gram-Positive Bacteria / Q000145:classification / Q000235:genetics* / Q000502:physiology; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010788:Photosynthesis / Q000235:genetics / Q000502:physiology; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics; D052817:Phototrophic Processes / Q000235:genetics / Q000502:physiology; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D045322:Photosynthetic Reaction Center Complex Proteins