Phthalate  degrading bacteria may be wide spread on Japanese coast.

Phthalate and phthalate esters are widely used in the manufacture of many products, including plastics, lubricants, textiles, paper, solvents and cosmetics and have recently become an environmental concern because of the potential of these compounds to act as carcinogenic, estrogenic and endocrine disruption (Matsumoto et al, 2008). These compounds have been found with a wide distribution in the marine environment, thought to originate from leaching of plastics into the ecosystem (Thompson et al, 2009). Many biodegrading microorganisms have been isolated and degradation pathways have been extensively investigated, but isolation of these microorganisms comes mainly from soil and freshwater systems and only two from the marine environment (Gu et al, 2009; Wang et al, 2008).

Iwaki and colleagues collected samples from three locations from the Japanese coast line, specifically chosen because of their high plastic content. Colonies were grown and isolated prior to PCR analysis to determine the gene sequences for comparison with 16s rRNA clone libraries. Isolated colonies were then grown on agar containing 5mM of sodium phthalate to determine if utilisation of phthalate as a substrate was possible.

 Iwaki and colleagues demonstrated that it was possible for the isolated bacterial strains to grow on phthalate and dimethyl phthalate as a sole carbon source. Iwaki and colleagues also postulate that to the best of their knowledge this is the first time any phthalate degrading bacteria have been isolated that can use phthalate purely as a carbon source. The bacteria isolated came from two main groups the α-proteobacteria and the γ-proteobacteria, with the former being the most abundant. Many strains were observed to be affiliated or related to the Rhodobacteraceae and some isolates represented new species. The isolates were most closely related to the genera Alteromonas, Citricella, Marinomonas, Marinovum, pelagibac, Rhodovulum, Sulifobacter, Thalassobius, Thalassococcus, thalassospira and Tropicibacter . Following this discovery Iwaki and colleagues suggested that many uncharacterised aromatic compound degrading bacteria may be present in the Japanese sea.   What is particularly interesting is the diversity of bacteria that seem to be able to degrade phthalate and also that these organisms differ completely from their freshwater and soil contemporaries. Another very interesting finding in this investigation was that all 11 genera seemed to share a common mechanism for the degradation of phthalate, all phthalate rings were hydroxylated at positions 4 & 5. To confirm this Iwaki and colleagues performed PCR amplification and analysis of the potential gene encoding 4,5-dihydroxyphthalate decarboxylase which is the key enzyme in phthalate degradation. This was confirmed and it is suggested that the high similarity of genes encoding for the phthalate degradation enzyme and the fact that most were isolated from the same family (Rhodobacteraceae), is suggestive of the fact that the mechanism comes from a common ancestor.

This was a very interesting study that has a lot of implications for bioremediation in the marine environment. The potential for this gene to be transferred by horizontally is also possible in natural systems, so it may be quite wide spread. I would have thought that if this gene could be isolated and transferred via plasmid to other bacteria, then there could be used for this gene in biotechnology. It also gives hope that naturally occurring processes could be ‘up regulating’ to mitigate some of our mistakes.

Very interesting study.      

REVIEWED: Iwaki. H., Nishimura. A., Hasegawa. Y., (2012). Isolation and characterisation of marine bacteria capable of utilising phthalate. World J  Microbial Biotech. 28: 1321-1325.

Gu JG, Han BP, Duan SS, Zhao ZY, Wang YP (2009) Degradation of the endocrine-disrupting dimethyl phthalate carboxylic ester by Sphingomonas yanoikuyae DOS01 isolated from the South China Sea and the biochemical pathway. Inter of Biodete& Biodegrad 63:450–455.

 

Matsumoto M, Hirata-Koizumi M, Ema M (2008) Potential adverse effects of phthalic acid esters on human health: a review of recent studies on reproduction. Regul Toxicol Pharmacol 50:37–49

 

Thompson RC, Moore CJ, vom Saal FS, Swan SH (2009) Plastics, the environment and human health: current consensus and future trends. Philos Trans R Soc Lond B Biol Sci 364:2153–2166.

 

Wang Y, Yin B, Hong Y, Yan Y, Gu JD (2008) Degradation of dimethyl carboxylic phthalate ester by Burkholderia cepacia DA2 isolated from marine sediment of South China Sea. Ecotoxicology. 17:845–852.

 

http://link.springer.com/article/10.1007%2Fs11274-011-0925-x?LI=true