Impact of natural oil and higher hydrocarbons on microbial diversity, distribution, and activity in Gulf of Mexico cold-seep sediments

Anaerobic degradation of propane and butane by sulfate-reducing bacteria enriched from marine hydrocarbon cold seeps

“…The results show that these microorganisms were apparently specialized, capable of degrading only propane and butane, similar to strain BuS5. This further supports in situ observations reporting that propane and butane appeared to be biologically degraded in oil and gas reservoirs (James and Burns, 1984;Boreham et al, 2001;Head et al, 2003;Larter et al, 2005) and at marine hydrocarbon-rich sites (Orcutt et al, 2010;Quistad and Valentine, 2011), whereas ethane, isobutane and pentane appeared rather resistant to degradation.…”

“…The cold-adapted gaseous alkane degraders described here are part of the DesulfosarcinaDesulfococcus group within the Deltaproteobacteria, which are found in relatively high abundance at gas and oil hydrocarbon seeps, very often reaching over 10% of the total free cells (for example, Orcutt et al, 2010;Kleindienst et al, 2012). Sulfatereduction rates determined at such sites often exceeded the rates attributed to anaerobic oxidation of methane by several fold (Bowles et al, 2011), and have been proposed to be due to oxidation of hydrocarbons other than methane, including shortchain alkanes Kallmeyer and Boetius 2004;Orcutt et al, 2005Orcutt et al, , 2010Niemann et al, 2006;Kleindienst et al, 2012).…”

“…Prop12-GMe clone 235 and But12-HyR clone 303 shared 95.5% sequence identity and were closely related to strain BuS5 (93.1% and 94.5%,respectively) and to the dominant phylotype in the enrichment culture But12-GMe (94.3% and 95.3%, respectively;Kniemeyer et al, 2007) (Figure 4). Other close relatives include phylotypes retrieved from marine mud volcanoes (Heijs et al, 2007;Lö sekann et al, 2007), hydrocarbon seep-associated sediments (Orphan et al, 2001;Lloyd et al, 2006;Kleindienst et al, 2012) or marine sediments associated with gas hydrates Orcutt et al, 2010) (Figure 4). The high abundance of a distinct phylotype in each enrichment culture suggests that the corresponding microorganisms were most likely responsible for the degradation of propane or butane.…”

“…Geochemical studies of anoxic deep-sea sediments provided the first indications that propane and butane are also degraded under anoxic conditions, suggesting a significant influence on the carbon and sulfur cycles in hydrocarbon-impacted environments. These data include the 13 C-enrichment of propane and butane in sediment interstitial waters atop gas hydrates (Sassen et al, 2004) or at deep sea mud volcanoes (Mastalerz et al, 2009), sulfate-reduction rates much higher than could be accounted for by anaerobic oxidation of methane in hydrothermal sediments or at cold seeps Kallmeyer and Boetius, 2004;Orcutt et al 2004Orcutt et al , 2010Kleindienst et al, 2012), or the apparent consumption of shortchain alkanes at mud volcanoes (Niemann et al, 2006). In addition, oxidation of propane under anoxic conditions has been determined in sediments collected from marine gas seeps (Quistad and Valentine, 2011).…”

Archaea of the Miscellaneous Crenarchaeotal Group are abundant, diverse and widespread in marine sediments

“…Among the cold seep sites with shallow sulfate depletion investigated here, the four sites from Hydrate Ridge and site 156 from the Gulf of Mexico showed the lowest MCG abundance concurrent with extremely high rates of AOM and sulfate reduction (Boetius et al, 2000;Treude et al, 2003;Orcutt et al, 2010). An exception were 4.6 m-deep sediments from sites 371 and 372 at HMMV which showed a high MCG abundance together with the lowest microbial activity due to high fluid flow rates repressing sulfate penetration Niemann et al, 2006).…”