Streptomyces:Other Bits/An Introduction to Streptomyces

Other Bits - Streptomyces Introduction
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An Introduction to Streptomyces
 Practical Streptomyces Genetics  This book is the bible of Streptomyces work; a must have for any Streptomyces researcher. Written by team leaders of Streptomyces research at the John Innes Centre, Norwich Research Park, UK; it covers almost everything from basic information to maps of different strains, media and buffer recipes, genetics methods, metabolism, antibiotic production and development.

For further details and to acquire a copy, visit: http://www.jic.ac.uk/SCIENCE/molmicro/Strepmanual/Manual.htm Kieser-PracticalStreptomycesGenetics-2000

Kieser, T., Bibb, M.J., Buttner, M.J., Chater, K.F. & Hopwood, D.A., (2000). Practical Streptomyces Genetics. Norwich, UK: John Innes Foundation.

Genomes Several Streptomyces genomes have been sequenced and some mapped, various degrees of annotation apply to each.

Streptomyces ambofaciens

Streptomyces avermitilis MA-4860

Streptomyces coelicolor A3(2)

Streptomyces diversa / Streptomyces venezuelae

Streptomyces griseus

Streptomyces hygroscopicus 10-22

Streptomyces lividans 66 ZX7

Streptomyces noursei ATCC 11455

Streptomyces peucetius ATCC 27952

Streptomyces rimosus R6-501

Streptomyces scabies 87-22

 Actinobacteria  Streptomyces coelicolor is a member of the class of bacteria called the Actinobacteria (older name: Actinomycetes). A taxonomic classification is available from the Global Biodiversity Information Facility

For years this class of bacteria has been the centre of research and discussion due to their diversity and complex life cycles. Organisms are assigned to this class on the basis of their chemotaxonomy, their high G+C context and the similarities in the sequences of their 16S ribosomal ribonucleic acid Hain-IntJSystBacterio-1997. In the early steps of microbiology, many organisms now belonging to the class of Actinobacteria, such as Mycobacterium leprae were considered as species somewhere between fungi and bacteria Hopwood-Microbiology-1999. In the light of new discoveries such as the: composition of the Actinobacteria cell wall (like that of typical Gram positive bacteria); the fact that their nuclear material was not delimited by any membrane and from their genome context itself, they were characterised as bacteria. This gave biologists a great field of exploration for bacterial development. Unlike most bacteria, Streptomycetes possess linear chromosomes Lin-MolMicro-1993. The genome of Streptomyces coelicolor displays great similarity at gene to gene level with other important Actinomycetales. Examples such as Mycobacterium tuberculosis and Mycobacterium leprae, the causative agents of tuberculosis and leprosy respectively; making learning by genome comparison easier since Streptomyces coelicolor is non pathogenic Bentley-Nature-2002.

 Secondary Metabolism  The biochemistry of Streptomycetes is truly remarkable, considering their production of secondary metabolites, many of which account for almost half of all known antibiotics Berdy-ZAllgMikrobiol-1964. Many of these compounds have important applications in human medicine as antibacterial, antitumour and antifungal agents. Also, in agriculture these compounds act as growth promoters, agents for plant protection, antiparasitic agents and herbicides Hopwood-Biotechnology-1995. The onset of antibiotic production of Streptomyces cultures grown on agar usually coincides with the early stages of morphological differentiation. One of the best known and understood Streptomycetes is Streptomyces coelicolor A3(2). In May 2002 the complete genome sequence of this model Actinobacteria was published. It has a single linear chromosome, instead of a circular chromosome that is common to bacteria. The complete sequence reveals a length of 8,667,507bp, and 7,825 predicted genes making it one of the largest bacterial genomes sequenced to date. It is nearly twice the size of Escherichia coli Blattner-Science-1997, Bacillus subtilis Kunst-Nature-1997 and Mycobacterium tuberculosis (Cole, 1998). It also has a greater number of genes than the lower eukaryote Saccharomyces cerevisiae, which has 6,183 genes (http://www.yeastgenome.org/). These findings however, are not entirely surprising given that Streptomyces coelicolor has a complex life cycle and exists in an environment in which it must be able to constantly adapt. There are at least five distinct secondary metabolites in S.coelicolor and four of these have antibiotic activity: The coloured and visually detected actinorhodin (Act) and undecylprodigiosin (Red); methylenomycin (Mmy) and the calcium dependent antibiotic (CDA). The aromatic polyketide actinorhodin (Act) provides probably the best studied example of all Streptomyces antibiotics with its colour being dependent on the pH of the environment: blue in neutral and alkaline solutions and red in acidic. It was Act which gave the trigger for investigation as well as the name of Streptomyces coelicolor Hopwood-Microbiology-1999.

 The Life Cycle of Streptomyces coelicolor  '''Germination &rarr; Vegetative Growth &rarr; Aerial Growth &rarr; Sporulation The life cycle of Streptomyces begins with the germination of a single spore. This spore produces one or more multi-nucleoid filaments Hardisson-JGenMicrobio-1978. This will elongate and branch on the surface and into the culture medium to form a vegetative mycelium. Hyphal growth is by quasi-exponential growth kinetics Chater-AnnuRevMicrobio-1993. This complex network of filaments will continue penetrating the medium, utilising the available organic molecules with the use of extracellular hydrolytic enzymes. This motility of the Streptomyces vegetative filaments gives it a big advantage to other less motile bacteria when it comes to colonizing solid substrates in the soil. In response to appropriate signals, believed to include the exhaust of nutrient supplies in the surrounding environment, the substrate mycelium will break the surface barrier and aerial hyphae are formed. Aerial growth coincides with the onset of secondary metabolism in cultures grown on solid media Chater-TrendsGenet-1989. The continuation of the aerial growth is supported by the utilization of the vegetative mycelium. When the extension of the aerial hyphae stops; their multigenomic tips undergo synchronous, multiple septation to give rise to unigenomic prespore compartments Schwedock-MolMicro-1997 Ryding-MolMicro-1998. Mature spores are held together in chains of about 50 and they develop a characteristic grey pigment as they mature Davis-MolMicro-1990. Unlike the endospores of other Gram-positive bacteria, such as Bacillus and Clostridium, Streptomyces exospores are not resistant to extreme heat or pH and are less dormant; however, they are fairly resistant to desiccation.



 References 
 * 1) Streptomyces:ReferencesList


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