Streptomyces:Other Bits/An Introduction to Streptomyces
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'''<big>Secondary Metabolism</big>''' | '''<big>Secondary Metabolism</big>''' | ||
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| - | The biochemistry of Streptomycetes is truly remarkable, considering their production of secondary metabolites, many of which account for almost half of all known antibiotics <cite>Berdy- | + | The biochemistry of Streptomycetes is truly remarkable, considering their production of secondary metabolites, many of which account for almost half of all known antibiotics <cite>Berdy-ZAllgMikrobiol-1964</cite>. 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 <cite>Hopwood-Biotechnology-1995</cite>. |
The onset of antibiotic production of ''Streptomyces'' cultures grown on agar usually coincides with the early stages of morphological differentiation. | 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'' <cite>Blattner-Science-1997</cite>, ''Bacillus subtilis'' <cite>Kunst-Nature-1997</cite> 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. | 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'' <cite>Blattner-Science-1997</cite>, ''Bacillus subtilis'' <cite>Kunst-Nature-1997</cite> 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. | ||
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| - | The life cycle of ''Streptomyces'' begins with the germination of a single spore. This spore produces one or more multi-nucleoid filaments <cite>Hardisson- | + | The life cycle of ''Streptomyces'' begins with the germination of a single spore. This spore produces one or more multi-nucleoid filaments <cite>Hardisson-JGenMicrobio-1978</cite>. 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 <cite>Chater-AnnuRevMicrobio-1993</cite>. 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. | 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 <cite>Chater-TrendsGenet-1989</cite>. | 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 <cite>Chater-TrendsGenet-1989</cite>. | ||
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| - | [[Image: Streptomyces_Life_Cycle_(small).gif|frame|none| '''Figure 1.''' <br/> The life cycle of Streptomyces coelicolor. <br/> From a single spore a vegetative mycelium germinates, this is followed by aerial growth with the production of aerial hyphae. These hyphae in turn will undergo synchronous septation to produce unigenomic spore compartments, which will disperse and thus commence a new cycle <cite>McGregor- | + | [[Image: Streptomyces_Life_Cycle_(small).gif|frame|none| '''Figure 1.''' <br/> The life cycle of Streptomyces coelicolor. <br/> From a single spore a vegetative mycelium germinates, this is followed by aerial growth with the production of aerial hyphae. These hyphae in turn will undergo synchronous septation to produce unigenomic spore compartments, which will disperse and thus commence a new cycle <cite>McGregor-JGenMicrobio-1954</cite>.]] |
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Revision as of 10:01, 5 September 2007
Other Bits - Streptomyces Introduction
An Introduction to StreptomycesPractical Streptomyces Genetics
For further details and to acquire a copy, visit: http://www.jic.ac.uk/SCIENCE/molmicro/Strepmanual/Manual.htm [1] Kieser, T., Bibb, M.J., Buttner, M.J., Chater, K.F. & Hopwood, D.A., (2000).
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
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 [8].
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 [9]. 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 [10]. 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 [3].
Germination → Vegetative Growth → Aerial Growth → Sporulation
![Figure 1. The life cycle of Streptomyces coelicolor. From a single spore a vegetative mycelium germinates, this is followed by aerial growth with the production of aerial hyphae. These hyphae in turn will undergo synchronous septation to produce unigenomic spore compartments, which will disperse and thus commence a new cycle [21].](/wiki/Image:Streptomyces_Life_Cycle_%28small%29.gif) Figure 1. The life cycle of Streptomyces coelicolor. From a single spore a vegetative mycelium germinates, this is followed by aerial growth with the production of aerial hyphae. These hyphae in turn will undergo synchronous septation to produce unigenomic spore compartments, which will disperse and thus commence a new cycle [21].
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