Biodegradation of [D-Leu1] microcystin-LR by a bacterium isolated from sediment of Patos Lagoon estuary,Brazil

Background: toxic cyanobacterial blooms are recurrent in patos lagoon,in southern brazil. among cyanotoxins,[d-leu1] microcystin-lr is the predominant variant whose natural cycle involves water and sediment compartments. this study aimed to identify and isolate from sediment a bacterial strain capable of growing on [d-leu1] microcystin-lr. sediment and water samples were collected at two distinct aquatic spots: close to the oceanographic museum (p1),in rio grande city,and on são lourenço beach (p2),in são lourenço do sul city,southern brazil.methods: [d-leu1] microcystin-lr was isolated and purified from batch cultures ofmicrocystis aeruginosastrain rst9501. samples of water and sediment from rio grande and são lourenço do sul were collected. bacteria from the samples were allowed to grow in flasks containing solely [d-leu1] microcystin-lr. this strain named dmsx was isolated on agar msm with 8 g l-1glucose and further purified on a cyanotoxin basis growth. microcystin concentration was obtained by using the elisa immunoassay for microcystins whereas bacterial count was performed by epifluorescence microscopy. the genuspseudomonaswas identified by dna techniques.results: although several bacterial strains were isolated from the samples,only one,dmxs,was capable of growing on [d-leu1] microcystin-lr. the phylogenetic analysis of the 16s rrna gene from dmxs strain classified the organism aspseudomonas aeruginosa. dmxs strain incubated with [d-leu1] microcystin-lr lowered the amount of toxin from 1 μg.l-1to < 0.05 μg.l-1. besides,an increase in the bacterial count-from 71 × 105bacteria.ml-1to 117 × 105bacteria.ml-1-was observed along the incubation.conclusions: the use of bacteria isolated from sediment for technological applications to remove toxic compounds is viable. studies have shown that sediment plays an important role as a source of bacteria capable of degrading cyanobacterial toxins. this is the first brazilian report on a bacterium-of the genuspseudomonas-that can degrade [d-leu1] microcystin-lr,the most frequent microcystin variant in brazilian freshwaters. © 2015 lemes et al.; licensee biomed central.