Biology subjects

Bissett, A.

Publications and source records attributed to Bissett, A..

4 recordsLinked to original sources

bioRxiv2022

Defining marine bacterioplankton community assembly rules by contrasting the importance of environmental determinants and biotic interactions

Bacterioplankton communities play major roles in governing marine productivity and biogeochemical cycling, yet what drives the relative influence of the types of deterministic ecological processes which result in diversity patterns remains unclear. Here we examine how differing deterministic processes (environmental factors and biotic interactions) drive temporal dynamics of bacterioplankton diversity at three different oceanographic time-series locations, spanning 15 degrees of latitude, which are each characterized by different environmental conditions and varying degrees of seasonality. Monthly surface samples, collected over a period of 5.5 years, were analyzed using 16S rRNA amplicon sequencing. The high and mid-latitude sites of Maria Island and Port Hacking were characterized by high and intermediate levels of environmental heterogeneity respectively, with both alpha (local) diversity (72 % and 24 % of total variation) and beta diversity (32 % and 30 %) patterns within bacterioplankton assemblages primarily explained by environmental determinants, including day length, ammonium, and mixed layer depth. In contrast, at North Stradbroke Island, a sub-tropical location where environmental conditions are less seasonally variable, interspecific interactions were of increased importance in structuring bacterioplankton diversity (alpha diversity: 33 %; beta diversity: 26 %) with environment only contributing 11 and 13 % to predicting diversity, respectively. Our results demonstrate that bacterioplankton diversity is the result of both deterministic environmental and biotic processes and that the importance of these different deterministic processes varies, potential in response to environmental heterogeneity. ImportanceMarine bacterioplankton drives important biological processes, including the cycling of key nutrients or fixing atmospheric carbon. Therefore, to predict future climate scenarios its critical to model these communities accurately. Processes that drive bacterioplankton diversity patterns in the oceans however remain unresolved, with most studies focusing on deterministic environmental drivers, ie temperature or available inorganic nutrients. Biotic deterministic processes including interactions among individuals are also important for structuring diversity patterns, however, this is rarely included to predict bacterioplankton communities. We develop an approach for determining the relative contribution of environmental and potential biotic interactions that structure marine bacterioplankton at three series at different latitudes. Environmental factors best predicted temporal trends in bacterioplankton diversity at the two high latitude time series, while biotic influence was most apparent at the low latitude time series. Our results suggest environmental heterogeneity is an important attribute driving the contribution of varying deterministic influence of bacterioplankton diversity.

ecology↗

bioRxiv2022

The importance of environmental parameters and mixing zone in shaping estuarine microbial communities along a freshwater-marine gradient.

Microbial communities are important elements in the marine environment, contributing to nutrient cycling and biogeochemical processes. Estuaries comprise environments exhibiting characteristics from freshwater to marine, leading to distinct microbial communities across this environmental gradient. Here, we examine the spatial dynamics of microbial communities in Macquarie Harbour, an estuarine system on the West coast of Tasmania, Australia. Water was sampled along the estuary to explore the structure and composition of the microbial communities using 16S/18S rRNA gene amplicon sequencing. Multivariate analyses showed environmental variables and community compositions varying along a longitudinal (river to adjacent ocean) gradient at the surface. In the harbour, differences in the microbial community were observed between surface (0-1 m) and intermediate depths (4.5-11 m depth). The results of differential abundance, network and Partial Least Square analyses suggest that Macquarie Harbour is a mixing zone, where the distributions of archaeal, bacterial and eukaryotic communities are influenced by oceanic and riverine inputs. Coupled with the natural characteristics of the Harbour, the heterotrophic component of this microbial communities inhabiting the surface and intermediate waters may play important roles in the nutrient cycle in the studied area. These results provide critical insights into the Macquarie Harbour environment and the importance of understanding the role of microbial communities for similar systems elsewhere.

microbiology↗

bioRxiv2021

An ecological perspective on microbial genes of unknown function in soil

Genes that remain hypothetical, uncharacterized, and unannotated comprise a substantial portion of metagenomic datasets and are likely to be particularly prevalent in soils where poorly characterized taxa predominate. Documenting the prevalence, distribution, and potential roles of these genes of unknown function is an important first step to understanding their functional contributions in soil communities. We identified genes of unknown function from 50 soil metagenomes and analyzed their environmental distributions and ecological associations. We found that genes of unknown function are prevalent in soils, particularly fine-textured, higher pH soils that harbor greater abundances of Crenarchaeota, Gemmatimonadota, Nitrospirota, and Methylomirabilota. We identified 43 dominant (abundant and ubiquitous) gene clusters of unknown function and determined their associations with soil microbial phyla and other "known" genes. We found that these dominant unknown genes were commonly associated with microbial phyla that are relatively uncharacterized, with the majority of these dominant unknown genes associated with mobile genetic elements. This work demonstrates a strategy for investigating genes of unknown function in soils, emphasizes the biological insights that can be learned by adopting this strategy, and highlights specific hypotheses that warrant further investigation regarding the functional roles of abundant and ubiquitous genes of unknown function in soil metagenomes.

microbiology↗

bioRxiv2021

Next generation restoration metrics: Using soil eDNA bacterial community data to measure trajectories towards rehabilitation targets

In post-mining rehabilitation, successful mine closure planning requires specific, measurable, achievable, relevant and time-bound (SMART) completion criteria, such as returning ecological communities to match a target level of similarity to reference sites. Soil microbiota are fundamentally linked to the restoration of degraded ecosystems, helping to underpin ecological functions and plant communities. High-throughput sequencing of soil eDNA to characterise these communities offers promise to help monitor and predict ecological progress towards reference states. Here we demonstrate a novel methodology for monitoring and evaluating ecological restoration using three long-term (> 25 year) case study post-mining rehabilitation soil eDNA-based bacterial community datasets. Specifically, we developed rehabilitation trajectory assessments based on similarity to reference data from restoration chronosequence datasets. Recognising that many alternative options for microbiota data processing have potential to influence these assessments, we comprehensively examined the influence of standard versus compositional data analyses, different ecological distance measures, sequence grouping approaches, eliminating rare taxa, and the potential for excessive spatial autocorrelation to impact on results. Our approach reduces the complexity of information that often overwhelms ecologically-relevant patterns in microbiota studies, and enables prediction of recovery time, with explicit inclusion of uncertainty in assessments. We offer a step change in the development of quantitative microbiota-based SMART metrics for measuring rehabilitation success. Our approach may also have wider applications where restorative processes facilitate the shift of microbiota towards reference states.

ecology↗