Distinct bacterial communities in tropical island aquifers

Abstract

The groundwater biome is a poorly characterized habitat hypothesized to harbor uniquely diverse bacterial communities; the degree to which these communities differ from associated soils is a central question in environmental microbiology. We characterized the Bacterial community composition in 37 aquifer and 32 surface soil samples across the island of O'ahu, Hawai'i. Several bacterial phyla (Acetothermia, Omnitrophica, Parcubacteria, Peregrinibacteria) relatively abundant in the aquifer samples were rare to absent in the soils. Immense bacterial diversity detected in the deep aquifers indicates that these environments are not as homogenous as expected, but provide various niches and energy sources for wide variety of bacteria. A small proportion of OTUs were widespread in all the basal (0.63%) and all the dike aquifer (0.31%) samples. However, these core bacteria comprised an average of 31.8% (ranging 16.2%-62.0%) and 15.4% (0.1%-31.5%) of all sequences isolated from the basal and dike aquifers respectively. Bacterial community composition correlated significantly with the sodium, sulfate, potassium, total dissolved solids, nitrate, conductivity, and pH in the basal aquifers, while phosphate and bicarbonate levels were also highly important when dike water samples were included in the analyses. This was consistent with high relative abundance of putative chemolithoautoroph taxa in the aquifer communities relative to soils. Targeted molecular and culture-based fecal indicator microbial analyses indicated good water quality of aquifers. The dominance of unique, deeply branching lineages in tropical aquifers emphasizes a large adaptive potential in O'ahu's aquifers; variability among groundwater samples suggests that aquifer habitats are surprisingly variable potentially harboring a variety of chemolithotrophic energy sources. Although parallel analyses of conventional and alternative indicators indicated good groundwater quality, this study calls for groundwater monitoring programs which would consider public as well as ecosystem health.

Soil Bacterial and Fungal Communities Response Differently to Bombax Ceiba (Malvaceae) in a Traditional Agroforestry System

“…These results suggested that potassium was the most important factor affecting bacterial community in Bombax -rice agroforestry system. Similarly, a study in tropical island aquifers con rmed that potassium had most signi cant relationship with bacterial community (Kirs et al 2020).…”

Exposure Pathways of Nontuberculous Mycobacteria Through Soil, Streams, and Groundwater, Hawai'i, USA

“…There has been little prior characterization of the biota of Hawai'i groundwater, although one recent study has documented diverse bacterial communities on Oahu to the phylum or class level (Kirs et al., 2020). They noted that Actinobacteria , the phylum to which NTM belong, are present in nearly all groundwater, albeit at a relatively low mean abundance (2.2%) but are a major constituent (26%) of the soil biome.…”

“…In summary, mycobacteria are a significant, if minor component of Hawai'i aquifer and a major component of soil biomes (Kirs et al., 2020), and cell count and transport studies indicate up to >10 7 cells/ml of bacteria may be expected in fractured basalt. NTM are now known to exist in the riparian environments of Kauai and Oahu where cells may tend to bind with hematite (Glickman et al., 2020).…”

Groundwater microbial communities reflect geothermal activity on volcanic island

“…Large subsurface aquatic habitats, like the volcanic groundwater aquifers of Hawaiʻi, support diverse communities due to the unique microenvironments available (e.g., surfaces, biofilms, particles) providing various and overlapping redox potentials (Bethke et al., 2011; Seitzinger et al., 2006). The most common metabolic pathways in groundwater ecosystems are chemolithoautotrophic, often utilizing hydrogen (H), S, Fe, and manganese (Mn) with oxygen (O) and nitrate (NO 3 ) as the most widely used electron acceptors (Anantharaman et al., 2016; Kirs et al., 2020). On volcanic islands, S compounds are often contaminants in freshwater as sulfate ($$$ {\mathrm{SO}}_4^{2-} $$$), sulfides (S 2− ), polysulfides ($$$ {\mathrm{S}}_x{\mathrm{O}}_6^{2-} $$$), and thiosulfate ($$$ {\mathrm{S}}_2{\mathrm{O}}_3^{2-} $$$), sourced from geothermal activity or seawater inputs (Flynn et al., 2012; Stefánsson et al., 2011; Xu et al., 1998).…”