(High G+C Gram-Positive Bacteria)
The phylum Actinobacteria is made up of gram-positive organisms with a high mole% G+C composition (> 55% G+C). This group is comprised of 39 families and 130 genera making it one of the largest phyla within Bacteria. They encompass a wide range of morphology from coccoid (e.g. Micrococcus) or rod-coccoid (e.g. Arthrobacter), fragmenting hyphal forms (e.g. Nocardia) to those with permanent and highly differentiated branched mycelium (e.g. Streptomyces). Many of the Actinobacteria are spore forming which range from motile zoospores to specialized propagules. They are also physiologically very diverse as evidenced by their production of numerous extracellular enzymes and by the thousands of metabolic products (including antibiotics) they synthesize and excrete. Actinobacteria especially members of Streptomycetaceae are the major antibiotic producers in the pharmaceutical industry. However, a few Actinobacteria are important human, animal and plant pathogens. For example, Mycobacterium tuberculosis infection result in tuberculosis; Corynebacterium diphtheriae causes diphtheria; Propionibacteirum acnes is the causative agent of acne. Actinobacterial species are widely distributed in both terrestrial and aquatic ecosystems and they play an important role in decomposition and recycling of biomaterials. Although Actinobacteria from a distinct cluster in the 16S rRNA trees, no other reliable biochemical or molecular characteristics that are unique to this group are presently known. However, recent analyses of genomic sequences have led to identification of many conserved indels and unique proteins that are shared by either all Actinobacteria, or different subgroups of them, and provide important means for elucidating their taxonomy, phylogeny and unique biochemical and physiological characteristics.
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Selected References
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Gao,B. & Gupta,R.S. (2005). Conserved Indels in Protein Sequences that are Characteristic of the Phylum Actinobacteria. Int. J. Syst. Evol. Microbiol, 55: 2401-2412.
Gao, B., Parmanathan, R. and Gupta, R.S. (2006) Signature Proteins that are Distinctive Characteristics of Actinobacteria and Their Subgroups . Antonie van Leeuwenhoek, 90(1):69-91.
Goodfellow,M. & Williams,S.T. (1983). Ecology of Actinomycetes. Annual Review of Microbiology, 37, 189-216.
Hopwood,D.A. (1999). Forty years of genetics with Streptomyces: from in vivo through in vitro to in silico. Microbiology, 145, 2183-2202.
Ludwig,W. & Klenk,H.-P. (2001). Overview: A phylogenetic backbone and taxonomic framework for prokaryotic systamatics. In D.R.Boone & R.W.Castenholz (Eds.), Bergey's Manual of Systematic Bacteriology (pp. 49-65). Berlin: Springer-Verlag.
Roller C, Ludwig W, & Schleifer KH (1992). Gram-positive bacteria with a high DNA G+C content are characterized by a common insertion within their 23S rRNA genes. J.Gen.Microbiol, 138, 167-175.
Stackebrandt,E., Rainey,F.A., & WardRainey,N.L. (1997). Proposal for a new hierarchic classification system, Actinobacteria classis nov. Int. J. Syst. Evol. Microbiol, 47(2), 479-491.
Stackebrandt, E.and Schumann, P. (2000). Introduction to the Taxonomy of Actinobacteria. InM.Dworkin & et al (Eds.), The Prokaryotes: An Evolving Electronic Resource for the Microbiological Community New York: Springer-Verlag.
Sutcliffe,I.C. & Harrington,D.J. (2002). Pattern searches for the identification of putative lipoprotein genes in Gram-positive bacterial genomes. Microbiology, 148(Pt 7), 2065-2077.
Ventura, M., Canchaya, C., Fitzgerald, G. F., Gupta, R. S. and van Sinderen, D. (2006) Genomics as a means to understand bacterial phylogeny and ecological adaptation: the case of bifidobacteria. Antonie van Leeuwenhoek. Oct 26 (Epub) [Abstract]
Citation for this webpage:
Bacterial (Prokaryotic) Phylogeny Webpage (April 2007). http://www.bacterialphylogeny.com/index.html