Investigation into the microbial ecology and persistence of soil taxa through trace-gas oxidation in Tongariro National Park

Abstract

Cultivation-dependent and metagenomic surveys of bare, volcanic and hyperarid oligotrophic ecosystems have revealed surprisingly diverse microbial communities¹⁻⁴. The richness of Mt. Tongariro soil communities is surprising considering the extreme environmental parameters. Given that soil moisture on Mt. Tongariro is highly variable dependent on season, and both phototrophic Cyanobacteria and trace gas oxidising taxa from the phyla Actinobacteria, WPS-2 and AD3 are detected in these soils, it is postulated that these taxa alternate as the primary producers in these oligotrophic soils. In this scenario, cyanobacteria are the phototrophic backbone and trace-gas oxidisers use atmospheric trace gases (H₂, CO) as supplemental cell energy for mixotrophic metabolism to persist. Mt. Tongariro soil communities were shown to encode high affinity hydrogenases and carbon monoxide dehydrogenases, which are necessary for atmospheric oxidation of H₂ and CO. This thesis details the microbial ecology and effect of physicochemistry on the alpha and beta diversity of Mt. Tongariro soils. It also addresses microbial persistence by the use oxidation of trace gases H₂ and CO at 4 °C and 60 °C for the South, Red and Central Craters of Mt. Tongariro on the southernmost point of the Taupo Volcanic Centre (TVZ), and control soils from White Island (Whakaari), Mt. Urchin and Mt. Sugarloaf. This preliminary study uncovers the microbial ecology of Mt. Tongariro and other bare, high elevation control soils from around New Zealand. Although, more extensive testing is required such as testing isolated Mt. Tongariro strains to understand whether the thermophilic taxa present are capable of oxidising trace gas, or whether they harbour low affinity enzymes suited to elevated levels of CO and H₂. This study indicates that trace gas oxidation may be an important mechanism for persistence or a dependable source of supplemental energy to specific mixotrophic trace-gas oxidising taxa in all communities from bare, oligotrophic systems.