AUTHOR=Johnson David B.

TITLE=Acidophilic algae isolated from mine-impacted environments and their roles in sustaining heterotrophic acidophiles

JOURNAL=Frontiers in Microbiology

VOLUME=3

YEAR=2012

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2012.00325

DOI=10.3389/fmicb.2012.00325

ISSN=1664-302X

ABSTRACT=<p>Two acidophilic algae, identified as strains of <italic>Chlorella protothecoides</italic> var. <italic>acidicola</italic> and <italic>Euglena mutabilis</italic>, were isolated in pure culture from abandoned copper mines in Spain and Wales and grown in pH- and temperature-controlled bioreactors. The <italic>Chlorella</italic> isolate grew optimally at pH 2.5 and 30°C, with a corresponding culture doubling time of 9 h. The isolates displayed similar tolerance (10–50 mM) to four transition metals tested. Growth of the algae in liquid media was paralleled with increasing concentrations of dissolved organic carbon (DOC). Glycolic acid was identified as a significant component (12–14%) of total DOC. Protracted incubation resulted in concentrations of glycolic acid declining in both cases, and glycolic acid added to a culture of <italic>Chlorella</italic> incubated in the dark was taken up by the alga (~100% within 3 days). Two monosaccharides were identified in cell-free liquors of each algal isolate: fructose and glucose (<italic>Chlorella</italic>), and mannitol and glucose (<italic>Euglena</italic>). These were rapidly metabolized by acidophilic heterotrophic bacteria (<italic>Acidiphilium</italic> and <italic>Acidobacterium</italic> spp.) though only fructose was utilized by the more fastidious heterotroph “<italic>Acidocella aromatica.</italic>” The significance of algae in promoting the growth of iron- (and sulfate-) reducing heterotrophic acidophiles that are important in remediating mine-impacted waters (MIWs) is discussed.</p>