Biology subjects

Currie, K.

Publications and source records attributed to Currie, K..

3 recordsLinked to original sources

bioRxiv2023

Asgard archaea defense systems and their roles in the origin of immunity in eukaryotes

Immune systems are integral to survival against viral infection. Recently, dozens of new antiviral systems have been characterized in bacteria1. Some of these systems are present in eukaryotes and appear to have originated in prokaryotes. However, little is known about these defense mechanisms in archaea. Here, we identified 2,610 complete defense systems in archaea related to eukaryotes, the Asgardarchaeota2. These comprise 89 unique systems, including argonaute, NLR, mokosh, viperin, lassamu, and CBASS. Asgard viperin (asVip) and argonaute (asAgo) proteins are present at high frequencies compared to bacteria and have structural homology to eukaryotes. Phylogenetic analyses revealed asVips are ancestral eukaryotic proteins. Heterologous expression of asVips in bacteria, including the lineage closest to eukaryotes, Hodarchaeales, showed anti-phage activity. Eukaryotic- and bacterial-argonaute proteins appear to have originated in Asgardarchaeota and preserve ancient structural characteristics. asAgos have argonaute-PIWI domains which are key components of the RNA interference (RNAi) in eukaryotes. Characterization of hundreds of defense systems in the Asgardarchaeota revealed these archaea played important roles in the innovation of viral protection in eukaryotes. Given their relationship to eukaryotes, these defense systems may have applications in biomedicine and biotechnology.

microbiology↗

bioRxiv2021

Microbial rhodopsins are increasingly favored over chlorophyll in High Nutrient Low Chlorophyll waters

Microbial rhodopsins are simple light-harvesting complexes that, unlike chlorophyll photosystems, have no iron requirements for their synthesis and phototrophic functions. Here we report the first environmental concentrations of rhodopsin along the Subtropical Frontal Zone off New Zealand, where Subtropical waters encounter the iron-limited Subantarctic High Nutrient Low Chlorophyll (HNLC) region. Rhodopsin concentrations were highest in HNLC waters where chlorophyll-a concentrations were lowest. Furthermore, while the ratio of rhodopsin to chlorophyll-a photosystems was on average 20 along the transect, this ratio increased to over 60 in HNLC waters. We further show that microbial rhodopsins are abundant in both picoplankton (0.2-3m) and in the larger (>3m) size fractions of the microbial community containing eukaryotic plankton and/or particle-attached prokaryotes. These findings suggest that rhodopsin phototrophy could be critical for microbial plankton to adapt to resource-limiting environments where photosynthesis and possibly cellular respiration are impaired. Originality-Significance statementHigh Nutrient Low Chlorophyll (HNLC) regimes cover approximately 30% of the global ocean surface and play a crucial role in the Earths carbon cycle. Here we show that microbial rhodopsins are particularly abundant in a HNLC region of the Subantarctic ocean, where chlorophyll abundance is relatively low and photosynthesis and respiration might be impaired due to iron limitation. These data suggest that rhodopsin phototrophy can contribute significantly to the energy budgets of HNLC regions, capturing meaningful amounts of light that cannot be channeled through photosynthesis.

ecology↗

bioRxiv2017

Are oceanic fronts ecotones? Seasonal changes along the Subtropical Front show fronts as bacterioplankton transition zones but not diversity hotspots

Ecotones are regarded as diversity hotspots in terrestrial systems, but it is unknown if this \"ecotone effect\" occurs in the marine environment. Oceanic fronts are widespread mesoscale features, present in the boundary between different water masses, and are arguably the best potential examples of ecotones in the ocean. Here we performed the first seasonal study along an oceanic front, combining 16S rRNA gene sequencing coupled with a high spatial resolution analysis of the physical properties of the water masses. Using the Subtropical Frontal Zone off New Zealand we demonstrate that fronts delimit shifts in bacterioplankton community composition between water masses, but that the strength of this effect is seasonally dependent. While creating a transition zone where physicochemical parameters and bacterioplankton communities get mixed, this ecotone does not result in increased diversity. Thus unlike terrestrial ecotones, oceanic ecotones like fronts are boundaries but not hotspot of bacterioplankton diversity in the ocean.

microbiology↗