Cyanobacteria produce arsenosugars

Abstract

Environmental context. Although arsenic is known to accumulate in both marine and freshwater ecosystems, the pathways by which arsenic is accumulated and transferred in freshwater systems are reasonably unknown. This study revealed that freshwater cyanobacteria have the ability to produce arsenosugars from inorganic arsenic compounds. The findings suggest that not only algae, but cyanobacteria, play an important role in the arsenic cycle of aquatic ecosystems.Abstract. Metabolic processes of incorporated arsenate in axenic cultures of the freshwater cyanobacteria Synechocystis sp. PCC 6803 and Nostoc (Anabaena) sp. PCC 7120 were examined. Analyses of arsenic compounds in cyanobacterial extracts using a high-performance liquid chromatography-inductively coupled plasma mass spectrometry system showed that both strains have an ability to biotransform arsenate into oxo-arsenosugar-glycerol within 20 min through (1) reduction of incorporated arsenate to arsenite and (2) methylation of produced arsenite to dimethylarsinic acid by methylarsonic acid as a possible intermediate product. In addition, Synechocystis sp. PCC 6803 cells are able to biosynthesise oxoarsenosugar-phosphate from incorporated arsenate. These findings suggest that arsenosugar formation as well as arsenic methylation in cyanobacteria possibly play a significant role in the global arsenic cycle.

Biosynthesis of arsenolipids by the cyanobacterium Synechocystis sp. PCC 6803

“…The majority of the extractable arsenic in cells was As V for all treatments with smaller amounts of As III , DMA V , MA V , and arsenosugars being identified in wild type cells. Compared to other studies [4,22] with cultures of Synechocystis sp. PCC 6803, our results showed less DMA V or arsenosugars when cells were exposed to 100 mM As V .…”

“…Yin et al [22] prepared samples using 1 % HNO 3 and microwave treatments, in which the original arsenic species were chemically degraded to DMA V . [23] Miyashita et al [4] extracted samples by sonication with water. Arsenosugars may be degraded to DMA V during sonication.…”

“…The most abundant and common arsenic compounds are arsenobetaine, the major arsenical in marine animals, and arsenosugars, which are dominant in marine algae. [1] Arsenobetaine and arsenosugars have also been identified in freshwater [2][3][4] and terrestrial organisms, [5] but generally only at low concentrations.…”

“…A recent report [4] that the cyanobacterium Synechocystis sp. PCC 6803 is capable of producing arsenosugars has encouraged us to explore arsenic metabolism and genetic manipulation in this organism.…”

Genomic potential for arsenic efflux and methylation varies among global Prochlorococcus populations

“…PCC 6803 and Nostoc sp. PCC 7120 are also capable of producing arsenosugars (Miyashita et al, 2012). Recent work suggests that human ingestion of arsenosugars and arsenolipids might be harmful with potential for release of toxic metabolites with arsenolipids posing the potential for toxicity at levels comparable with inorganic arsenite (Harrington et al, 2008;Raml et al, 2009;Newcombe et al, 2010;Feldmann and Krupp, 2011;Leffers et al, 2013a, b;Meyer et al, 2014).…”