{"id":7763,"date":"2016-06-14T22:51:58","date_gmt":"2016-06-14T22:51:58","guid":{"rendered":"https:\/\/www.darkenergybiosphere.org\/?post_type=publication&#038;p=7752"},"modified":"2016-10-14T19:06:48","modified_gmt":"2016-10-14T19:06:48","slug":"variations-in-microbial-carbon-sources-and-cycling-in-the-deep-continental-subsurface","status":"publish","type":"publication","link":"https:\/\/www.darkenergybiosphere.org\/publication\/variations-in-microbial-carbon-sources-and-cycling-in-the-deep-continental-subsurface\/","title":{"rendered":"Variations in microbial carbon sources and cycling in the deep continental subsurface"},"content":{"rendered":"<p>Deep continental subsurface fracture water systems, ranging from 1.1 to 3.3\u00a0km below land surface (kmbls), were investigated to characterize the indigenous microorganisms and elucidate microbial carbon sources and their cycling. Analysis of phospholipid fatty acid (PLFA) abundances and direct cell counts detected varying biomass that was not correlated with depth. Compound-specific carbon isotope analyses (\u03b4<sup>13<\/sup>C and \u0394<sup>14<\/sup>C) of the phospholipid fatty acids (PLFAs) and carbon substrates combined with genomic analyses did identify, however, distinct carbon sources and cycles between the two depth ranges studied.<\/p>\n<p>In the shallower boreholes at circa 1\u00a0kmbls, isotopic evidence indicated microbial incorporation of biogenic CH<sub>4<\/sub> by the <em>in situ<\/em> microbial community. At the shallowest site, 1.05\u00a0kmbls in Driefontein mine, this process clearly dominated the isotopic signal. At slightly deeper depths, 1.34\u00a0kmbls in Beatrix mine, the isotopic data indicated the incorporation of both biogenic CH<sub>4<\/sub> and dissolved inorganic carbon (DIC) derived from CH<sub>4<\/sub> oxidation. In both of these cases, molecular genetic analysis indicated that methanogenic and methanotrophic organisms together comprised a small component (&lt;5%) of the microbial community. Thus, it appears that a relatively minor component of the prokaryotic community is supporting a much larger overall bacterial community in these samples.<\/p>\n<p>In the samples collected from &gt;3\u00a0kmbls in Tau Tona mine (TT107, TT109 Bh2), the CH<sub>4<\/sub> had an isotopic signature suggesting a predominantly abiogenic origin with minor inputs from microbial methanogenesis. In these samples, the isotopic enrichments (\u03b4<sup>13<\/sup>C and \u0394<sup>14<\/sup>C) of the PLFAs relative to CH<sub>4<\/sub> were consistent with little incorporation of CH<sub>4<\/sub> into the biomass. The most <sup>13<\/sup>C-enriched PLFAs were observed in TT107 where the dominant CO<sub>2<\/sub>-fixation pathway was the acetyl-CoA pathway by non-acetogenic bacteria. The differences in the \u03b4<sup>13<\/sup>C of the PLFAs and the DIC and DOC for TT109 Bh2 were \u223c\u221224\u2030 and 0\u2030, respectively. The dominant CO<sub>2<\/sub>-fixation pathways were 3-HP\/4-HB cycle\u00a0&gt;\u00a0acetyl-CoA pathway\u00a0&gt;\u00a0reductive pentose phosphate cycle.<\/p>\n","protected":false},"template":"","tags":[],"publication_type":[19],"_links":{"self":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication\/7763"}],"collection":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication"}],"about":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/types\/publication"}],"wp:attachment":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/media?parent=7763"}],"wp:term":[{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/tags?post=7763"},{"taxonomy":"publication_type","embeddable":true,"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication_type?post=7763"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}