Transformation of arsenic(V) by the fungus Fusarium oxysporum melonis isolated from the alga Fucus gardneri

Abstract

A fungus isolated from the macroalga Fucus gardneri was identified by using 28S rDNA sequence analysis, 99% similarity match, as Fusarium oxysporum meloni. The fungus was exposed to arsenic(V) (500 ppb) in artificial seawater to investigate the possibility that the fungus is the source of the metabolic activity that results in the presence of arsenosugars in the macroalga. High-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry was used to identify the arsenic species in the fungus, and in the growth medium. The fungus was able to accumulate arsenic(V) and an increase in arsenite and dimethylarsinate was also observed. Some reduction of arsenate led to a small increase of arsenite in the growth medium. The fungus does not seem to be involved with the accumulation of arsenosugars by the Fucus.

Capability of Pentavalent Arsenic Bioaccumulation and Biovolatilization of Three Fungal Strains under Laboratory Conditions

“…70 days to volatilize all of the As in the culture system (2500 lg), which was an intriguingly biological response to As exposure for F. oxysporum. Granchinho et al [12] suggested that F. oxysporum was capable of accumulating As(V) from the surrounding medium and transforming it into As(III) and DMA (dimethylarsinite), with the latter entity being an easily volatile arsenide. The present investigation demonstrated that F. oxysporum behaved in a similar manner to that predicted by Granchinho et al [12].…”

“…Granchinho et al [12] suggested that F. oxysporum was capable of accumulating As(V) from the surrounding medium and transforming it into As(III) and DMA (dimethylarsinite), with the latter entity being an easily volatile arsenide. The present investigation demonstrated that F. oxysporum behaved in a similar manner to that predicted by Granchinho et al [12]. No As was observed in fungi controls which were cultivated in the absence of As.…”

Cyanobacteria produce arsenosugars

“…Microbes living in marine environments are likely to have an ability to produce arsenosugars, [16,17] and several studies have centred on the role of marine microbes in the possible production and biodegradation of arsenosugars. [18][19][20] Thus, identification of As metabolites in microbes grown in pure culture, such as eukaryotic microalgae and prokaryotic cyanobacteria, has been performed to confirm biotransformation mechanisms of As after experimental exposure to inorganic As species. Previous reports generally indicate that microalgae (not only marine species (Dunaliella tertiolecta and Phaeodactylum tricornutum) [17] but also freshwater ones (Chlorella vulgaris, [21] Chlorella sp., [22] Chlamydomonas reinhardtii [23,24] and Monoraphidium arcuatum [22] ) can produce arsenosugars from incorporated As V by reduction and methylation processes, and that cyanobacteria (freshwater species, Microcystis sp.…”

Biomethylation and bioaccumulation of arsenic(V) by marine alga Fucus gardneri

“…It is conceivable that this fungus, identified as F. oxysporum melonis by sequencing of its 28S ribosomal RNA gene, is responsible for the biotransformation of arsenic species. 18 Independent studies showed that the isolated fungus is able to convert arsenate to arsenite and DMA; 18 however, the relative amounts of these arsenicals produced by the fungus was about 1000 times lower than that produced by the Fucus. Thus we conclude that, in this experiment, we are observing changes attributable mainly to the algae, even though it is difficult to predict the results of a possible joint interaction of the Fucus and the fungus in a symbiotic relationship.…”

“…Antibiotics, antimycotics and other decontamination procedures were included in an attempt to make sure no living organisms, other than the Fucus, were involved in the exposure experiment. However, the treatment was not completely successful, because a fungus (Fusarium oxysporum melonis) 18 was observed to grow with the Fucus during both the acclimation and exposure experiments. Nonetheless, the contamination due to bacteria was at a minimum, since no bacterial infection was in evidence.…”