Biology subjects

Southam, G.

Publications and source records attributed to Southam, G..

2 recordsLinked to original sources

bioRxiv2020

Microbial activated mineral weathering and cementation as precursors to hardpan formation and heavy metal encapsulation in sulfidic tailings

Extensive mineral weathering and formation of large amounts of Fe-rich secondary mineral gels have been identified as precursors critical to forming massive hardpan caps in the surface layers of sulfidic tailings. However, how to initiate and accelerate these precursor processes remains to be established before developing this hardpan-based novel method to rehabilitate sulfidic tailings landscapes. In a 5-month microcosm experiment, the present study has demonstrated the concept of bio-engineering sulfidic tailings by inoculating Fe/S-oxidizing bacterial consortium to accelerate the weathering of sulfides and other Si-rich minerals for mineral gels formation. Synchrotron-based X-ray absorption fine structure spectroscopy (XAFS) demonstrated that the weathering of pyrite and biotite-like minerals was rapidly accelerated by the presence of Fe/S-oxidizing bacterial consortium. The microbial process and associated mineral transformation led to the formation of critical precursor mineral gels, i.e., jarosite-like minerals, as indicators of the onset of hardpan formation. In the meantime, the labile Zn liberated in the weathering was encapsulated in the jarosite-like minerals as revealed by X-ray fluorescence microscopy (XFM). This concept-proven bio-engineering process is ready to be scaled up in further studies under field conditions to develop an alternative hardpan-based method to cover and rehabilitate sulfidic tailing landscapes. TOC Art O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=145 SRC="FIGDIR/small/285858v1_ufig1.gif" ALT="Figure 1"> View larger version (83K): org.highwire.dtl.DTLVardef@fc0292org.highwire.dtl.DTLVardef@10ce8c7org.highwire.dtl.DTLVardef@868a63org.highwire.dtl.DTLVardef@e77d57_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2020

A widely distributed hydrogenase oxidises atmospheric H2 during bacterial growth

Diverse aerobic bacteria persist by consuming atmospheric hydrogen (H2) using group 1h [NiFe]-hydrogenases. However, other hydrogenase classes are also distributed in aerobes, including the group 2a [NiFe]-hydrogenase. Based on studies focused on Cyanobacteria, the reported physiological role of the group 2a [NiFe]-hydrogenase is to recycle H2 produced by nitrogenase. However, given this hydrogenase is also present in various heterotrophs and lithoautotrophs lacking nitrogenases, it may play a wider role in bacterial metabolism. Here we investigated the role of this enzyme in three species from different phylogenetic lineages and ecological niches: Acidithiobacillus ferrooxidans (phylum Proteobacteria), Chloroflexus aggregans (phylum Chloroflexota), and Gemmatimonas aurantiaca (phylum Gemmatimonadota). qRT-PCR analysis revealed that the group 2a [NiFe]-hydrogenase of all three species is significantly upregulated during exponential growth compared to stationary phase, in contrast to the profile of the persistence-linked group 1h [NiFe]-hydrogenase. Whole-cell biochemical assays confirmed that all three strains aerobically respire H2 to sub-atmospheric levels, and oxidation rates were much higher during growth. Moreover, the oxidation of H2 supported mixotrophic growth of the carbon-fixing strains C. aggregans and A. ferrooxidans. Finally, we used phylogenomic analyses to show that this hydrogenase is widely distributed and is encoded by 13 bacterial phyla. These findings challenge the current persistence-centric model of the physiological role of atmospheric H2 oxidation and extends this process to two more phyla, Proteobacteria and Gemmatimonadota. In turn, these findings have broader relevance for understanding how bacteria conserve energy in different environments and control the biogeochemical cycling of atmospheric trace gases.

microbiology↗