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Microbial sunscreens.

Siezen RJ - Microb Biotechnol (2011)

View Article: PubMed Central - PubMed

Affiliation: Kluyver Centre for Genomics of Industrial Fermentation, Delft, the Netherlands. r.siezen@cmbi.ru.nl

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In response to intense solar radiation, cyanobacteria and some other microorganisms have evolved a variety of defence mechanisms including the biosynthesis of UV‐absorbing/screening compounds such as mycosporine‐like amino acids (MAAs) and scytonemin... So far, scytonemin has been found to be produced mainly by cyanobacteria (Fig.  1), while mycosporine and MAAs are widespread and are accumulated by a range of microorganisms, prokaryotic (cyanobacteria) as well as eukaryotic (microalgae, yeasts and fungi), and a variety of marine macroalgae, corals and other marine life forms... A brief overview is given here to wet your appetite... Mycosporines and MAAs are colourless compounds found intracellularly in many marine and freshwater organisms... Cyanobacteria make primarily mycosporine‐glycine, shinorine, porphyra‐334 and palythinol, while fungi make mainly mycosporine‐glutaminol/glutamicol‐glucoside and macroalgae make various other MAAs... MAAs found in higher animals are derived from their algal diet... Recently, the initial steps in the biosynthesis of mycosporines and MAAs in Anabaena variabilis were elegantly elucidated... A cluster of four genes (Fig.  3A) was found to be responsible for conversion of the common pentose phosphate pathway intermediate sedoheptulose 7‐phosphate into shinorine (Fig.  3B)... In cyanobacteria, all gene clusters contain the first three genes to generate the main intermediate mycosporine‐glycine, while additional genes vary... Cyanobacteria produce the indole alkaloid scytonemin as part of their response strategy for survival in environmentally stressed conditions, particularly in pulsed‐irradiation conditions such as in hot and cold deserts... It is found as a yellow (oxidized) to red‐brown (reduced), lipid‐soluble pigment in the extracellular sheaths or other polysaccharide structures (Fig.  1)... In this gene cluster there is a redundant set of genes coding for shikimic acid and aromatic acid biosynthesis enzymes, leading to the production of tryptophan and p‐hydroxyphenylpyruvate, which are the likely precursors of scytonemin (Fig.  4)... The fact that gene clusters for both scytonemin and MAAs biosynthesis are present in the sequenced genomes of Nostoc, Anabaena, Cyanothece, Nodularia and Lyngbya strains (Table 1) suggests that it is common for cyanobacteria to produce both sunscreen compounds, giving full protection over a wide UV radiation range.

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Mentions: The scytonemin biosynthesis pathway and associated genes have been partially elucidated in the cyanobacterium Nostoc punctiforme ATCC29133 (Soule et al., 2007; Balskus and Walsh, 2008; 2009; Soule et al., 2009a). An 18‐gene cluster responsible for biosynthesis was identified and shown to be specifically induced by UV‐A radiation (Fig. 4) (Soule et al., 2007; 2009a). Six consecutive genes coined scyA–scyF with no previously known function are likely involved in assembly of scytonemin. In this gene cluster there is a redundant set of genes coding for shikimic acid and aromatic acid biosynthesis enzymes, leading to the production of tryptophan and p‐hydroxyphenylpyruvate, which are the likely precursors of scytonemin (Fig. 4). A tentative scheme of biosynthesis steps and a working model for the cellular localization of gene products have been proposed (Soule et al., 2009b; Rastogi et al., 2010). Genome data mining subsequently identified highly similar gene clusters in the cyanobacteria Anabaena, Lyngbya, Nodularia, Cyanothece and Chlorogleopsis, and two linked smaller gene clusters probably also involved in biosynthesis and regulation, based on synteny and sequence conservation (Fig. 5) (Soule et al., 2009b). Scytonemin biosynthesis could not be induced by UV‐A in all these strains, suggesting that some gene clusters have become inactive, possibly due to long laboratory cultivation (Soule et al., 2009b).


Microbial sunscreens.

Siezen RJ - Microb Biotechnol (2011)

© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3815790&req=5

Mentions: The scytonemin biosynthesis pathway and associated genes have been partially elucidated in the cyanobacterium Nostoc punctiforme ATCC29133 (Soule et al., 2007; Balskus and Walsh, 2008; 2009; Soule et al., 2009a). An 18‐gene cluster responsible for biosynthesis was identified and shown to be specifically induced by UV‐A radiation (Fig. 4) (Soule et al., 2007; 2009a). Six consecutive genes coined scyA–scyF with no previously known function are likely involved in assembly of scytonemin. In this gene cluster there is a redundant set of genes coding for shikimic acid and aromatic acid biosynthesis enzymes, leading to the production of tryptophan and p‐hydroxyphenylpyruvate, which are the likely precursors of scytonemin (Fig. 4). A tentative scheme of biosynthesis steps and a working model for the cellular localization of gene products have been proposed (Soule et al., 2009b; Rastogi et al., 2010). Genome data mining subsequently identified highly similar gene clusters in the cyanobacteria Anabaena, Lyngbya, Nodularia, Cyanothece and Chlorogleopsis, and two linked smaller gene clusters probably also involved in biosynthesis and regulation, based on synteny and sequence conservation (Fig. 5) (Soule et al., 2009b). Scytonemin biosynthesis could not be induced by UV‐A in all these strains, suggesting that some gene clusters have become inactive, possibly due to long laboratory cultivation (Soule et al., 2009b).

View Article: PubMed Central - PubMed

Affiliation: Kluyver Centre for Genomics of Industrial Fermentation, Delft, the Netherlands. r.siezen@cmbi.ru.nl

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

In response to intense solar radiation, cyanobacteria and some other microorganisms have evolved a variety of defence mechanisms including the biosynthesis of UV‐absorbing/screening compounds such as mycosporine‐like amino acids (MAAs) and scytonemin... So far, scytonemin has been found to be produced mainly by cyanobacteria (Fig.  1), while mycosporine and MAAs are widespread and are accumulated by a range of microorganisms, prokaryotic (cyanobacteria) as well as eukaryotic (microalgae, yeasts and fungi), and a variety of marine macroalgae, corals and other marine life forms... A brief overview is given here to wet your appetite... Mycosporines and MAAs are colourless compounds found intracellularly in many marine and freshwater organisms... Cyanobacteria make primarily mycosporine‐glycine, shinorine, porphyra‐334 and palythinol, while fungi make mainly mycosporine‐glutaminol/glutamicol‐glucoside and macroalgae make various other MAAs... MAAs found in higher animals are derived from their algal diet... Recently, the initial steps in the biosynthesis of mycosporines and MAAs in Anabaena variabilis were elegantly elucidated... A cluster of four genes (Fig.  3A) was found to be responsible for conversion of the common pentose phosphate pathway intermediate sedoheptulose 7‐phosphate into shinorine (Fig.  3B)... In cyanobacteria, all gene clusters contain the first three genes to generate the main intermediate mycosporine‐glycine, while additional genes vary... Cyanobacteria produce the indole alkaloid scytonemin as part of their response strategy for survival in environmentally stressed conditions, particularly in pulsed‐irradiation conditions such as in hot and cold deserts... It is found as a yellow (oxidized) to red‐brown (reduced), lipid‐soluble pigment in the extracellular sheaths or other polysaccharide structures (Fig.  1)... In this gene cluster there is a redundant set of genes coding for shikimic acid and aromatic acid biosynthesis enzymes, leading to the production of tryptophan and p‐hydroxyphenylpyruvate, which are the likely precursors of scytonemin (Fig.  4)... The fact that gene clusters for both scytonemin and MAAs biosynthesis are present in the sequenced genomes of Nostoc, Anabaena, Cyanothece, Nodularia and Lyngbya strains (Table 1) suggests that it is common for cyanobacteria to produce both sunscreen compounds, giving full protection over a wide UV radiation range.

Show MeSH
Related in: MedlinePlus