Arsenate reducing bacteria isolated from the marine sponge Theonella swinhoei: Bioremediation potential.

Arsenic (As) contamination of freshwater resources constitutes a major environmental issue affecting over 200 million people worldwide. Although the use of microorganisms for the bioremediation of As has been well studied, only very few candidates have been identified to date. Here, we investigated bacteria associated with the Red Sea sponge Theonella swinhoei and their potential to reduce As in a low-salinity liquid medium. This Indo-Pacific common sponge has been shown to hyper-accumulate As, at an average concentration of 8600 mg/g-1 in an environment uncontaminated by arsenic or barium. Four isolated strains of bacteria exhibited arsenic reduction potential by transforming inorganic As in the form of arsenate (iAsV) to arsenite (iAsIII). Two of these isolates were identified as Alteromonas macleodii and Pseudovibrio ascidisceicola, and the other two isolates, both belonging to the same species, were identified as Pseudovibrio denitrificans. The four isolates were then cultured in a low-salinity iAsV-rich medium (5 mM) and As concentration was measured over time using a specifically designed high-performance liquid chromatograph coupled to a mass spectrometer (HPLC-MS). Out of the four isolates, A. macleodii and P. ascidisceicola grew successfully in a low-salinity liquid medium and reduced AsV to AsIII at an average rate of 0.094 and 0.083 mM/h, respectively, thereby demonstrating great potential for the bioremediation of As-contaminated groundwater.

Theonellamides J and K and 5-cis-Apoa-theopalauamide, Bicyclic Glycopeptides of the Red Sea Sponge Theonella swinhoei.

Theonella swinhoei is a fairly common inhabitant of reefs throughout the Indian and Pacific Oceans. Metabolomic analyses of samples of T. swinhoei collected in different depths in the Gulf of Aqaba revealed two chemotypes differing in the profiles of the theonellamides they produce, some of which seem to be unknown. Driven by this finding, we examined a sample of T. swinhoei collected more than 40 years ago in the southern part of the Gulf of Aqaba. Large-scale extract of this sample yielded four theonellamides, the known theopalauamide (4), as the major component, and three new metabolites, theonellamide J (1), 5-cis-Apoa-theopalauamide (2), and theonellamide K (3), as the minor components. The planar structure of these complex cyclic glycopeptides was elucidated by combination of 1D and 2D NMR techniques and HRESIMS. The absolute configuration of the amino acids was established by Marfey's and advanced Marfey's methods, and the absolute configuration of its galactose unit using "Tanaka's method" for monosaccharides. The biological activity of the pure compounds was tested for antibacterial activity and for cytotoxicity to HTC-116 cell line. The compounds presented significant cytotoxicity against the HTC-116 cell line, illuminating the importance of the Apoa subunit for the activity.