The Hawaiian Archipelago: A Microbial Diversity Hotspot

Abstract

The Hawaiian Archipelago is a "biodiversity hotspot" where significant endemism among eukaryotes has evolved through geographic isolation and local topography. To address the absence of corresponding region-wide data on Hawaii's microbiota, we compiled the first 16S SSU rDNA clone libraries and cultivated bacteria from five Hawaiian lakes, an anchialine pool, and the Lō'ihi submarine volcano. These sites offer diverse niches over approximately 5000 m elevation and approximately 1150 nautical miles. Each site hosted a distinct prokaryotic community dominated by Bacteria. Cloned sequences fell into 158 groups from 18 Bacteria phyla, while seven were unassigned and two belonged in the Euryarchaeota. Only seven operational taxonomic units (each OTU comprised sequences that shared > or =97% sequence identity) occurred in more than one site. Pure bacterial cultures from all sites fell into 155 groups (each group comprised pure cultures that shared > or =97% 16S SSU rDNA sequence identity) from 10 Bacteria phyla; 15 Proteobacteria and Firmicutes were cultivated from more than one site. One hundred OTUs (60%) and 52 (33.3%) cultures shared <97% 16S SSU rDNA sequence identity with published sequences. Community structure reflected habitat chemistry; most delta-Proteobacteria occurred in anoxic and sulfidic waters of one lake, while beta-Proteobacteria were cultivated exclusively from fresh or brackish waters. Novel sequences that affiliate with an Antarctic-specific clade of Deinococci, and Candidate Divisions TM7 and BRC1, extend the geographic ranges of these phyla. Globally and locally remote, as well as physically and chemically diverse, Hawaiian aquatic habitats provide unique niches for the evolution of novel communities and microorganisms.

Arcobacter halophilus sp. nov., the first obligate halophile in the genus Arcobacter

“…A water sample was collected directly into a sterile 1 litre NalgeneH bottle from the surface of the hypersaline lagoon at the centre of Laysan Atoll (25 u 469 N, 171 u 449 W) in the north-western Hawaiian Islands in October 2000 (Donachie et al, 2004a). Salinity was determined with an AGE model 2100 Minisal salinometer calibrated against International Association for the Physical Sciences of the Ocean standard (Wormley) sea water.…”

“…During a molecular and cultivation-based survey of prokaryotes from little-explored aquatic habitats in Hawai'i, Donachie et al (2004a) cultivated aerobic heterotrophs from the hypersaline lagoon on Laysan Atoll, including novel species (Donachie et al, 2004b). Laysan Atoll is already recognized for its unique flora and fauna, and hosts over 40 endemic insect and bird species (Ely & Clapp, 1973;Bakus, 1978).…”

Culture clash: challenging the dogma of microbial diversity

“…Such assumptions, however, often do not hold true. One such study of microbial diversity in Hawaiian lakes and at the Hawaiian submarine volcano Lō'ihi, recorded 158 operational taxonomic units (OTUs) from 18 Bacteria phyla, with seven unassigned and two Euryarchaeota (Donachie et al, 2004a), where sequences in each OTU shared X97% 16S rDNA insert sequence identity. Bacteria cultivated from the same samples were grouped into 155 'taxa' from 10 phyla, with cultures in each taxon sharing X97% 16S rDNA sequence identity.…”

“…We posit that although there may not be one consistent cause, preparation steps in the molecular approach may introduce some biases. For example, DNA might not be extracted from difficult to lyse cells (for example, Firmicutes) during community DNA extraction (Donachie et al, 2004a). Conversely, these authors dismissed a 'lack of primer specificity' because pure cultures in their study were sequenced with the same primers used in clone library construction.…”

“…OTU and culture group numbers are presented here as reported in the original paper. The seven habitats shown are (1) endodontic pathogenic oral biofilms (Munson et al, 2002); (2) exodontic oral biofilms (Munson et al, 2004); (3) Hawaiian lakes and Lō'ihi (Donachie et al, 2004a); (4) rhizoplane (Kaiser et al, 2001); (5) bird feathers (Shawkey et al, 2005); (6) ocean (Eilers et al, 2000); (7) hypersaline salterns (Maturrano et al, 2006). molecular methods alone can detect 'unculturable' (i.e., previously uncultivated) bacteria.…”