Succession of bacterial community structure during the early stage of biofilm development in the Antarctic marine environment

<p>Antarctic sea ice is an important feature of the southern ocean where at its maximum it can cover 8 % of the Southern Hemisphere. It provides a stable environment for the colonisation of diverse and highly specialised microbes which play a central role in the assimilation and regulation of energy through the Antarctic food web. Polar environments are sensitive to changes in the environment. Small changes in temperature can have large effects on sea ice thickness and extent and Antarctic sea ice cover is expected to shrink by 25 % over the next century. It is unknown how the sea ice microbiota will respond. In order to understand the effects of climate change on the sea ice ecosystem it is necessary to obtain information about the community structure, function and diversity and their reactions with the environment. Studies have focused on algal diversity and physiology in Antarctic sea ice and in comparison studies on the prokaryotic community are few. Although prokaryotic diversity has been investigated using clone libraries and culture based methods, it is likely that certain species have still not been described. Almost nothing is known about the Antarctic sea ice bacterial community spatial and temporal dynamics under changing abiotic and biotic conditions or their role in biogeochemical cycles. This is the first study linking Antarctic bacterial communities to function by using statistics to investigate the relationships between environmental variables and community structure. Bacterial community structure was investigated by extracting both the DNA and RNA from the environment to understand both the metabolically active (RNA) and total (DNA) bacterial community. The thickness of the sea ice and nutrient concentrations were key factors regulating bacterial community composition in Antarctic sea ice. Sea ice thickness is likely to have an effect on the physiological responses of algae leading to changes in photosynthate concentrations and composition of dissolved organic matter (DOM). Further investigations into the relationships between enzymatic activity and community structure revealed that the composition of the DOM drove variation between bacterial communities. There was no relationship between bacterial abundance and chlorophyll-a (as a measure of algal biomass), suggesting a un-coupling of the microbial loop. However bacteria were actively involved in the hydrolysis of polymers throughout the sea ice core. Investigations using quantitative PCR (qPCR) found that the functional genes involved in denitrification and light energy utilisation were in low abundance therefore these processes are minor in Antarctic sea ice. These results confirm that sea ice bacteria are predominantly heterotrophs and have a major role in the cycling of carbon and nitrogen through the microbial loop ...</p>

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Bacterial community structure of early-stage biofilms is dictated by temporal succession rather than substrate types in the southern coastal seawater of India

PLoS ONE ◽

10.1371/journal.pone.0257961 ◽

2021 ◽

Vol 16 (9) ◽

pp. e0257961

Author(s):

T. J. Sushmitha ◽

Meora Rajeev ◽

P. Sriyutha Murthy ◽

S. Ganesh ◽

Subba Rao Toleti ◽

...

Keyword(s):

Bacterial Community ◽

Marine Environment ◽

Bacterial Communities ◽

Early Stage ◽

Substrate Material ◽

Community Succession ◽

Temporal Succession ◽

Biofilm Development ◽

Bacterial Groups ◽

Planktonic Community

Bacterial communities colonized on submerged substrata are recognized as a key factor in the formation of complex biofouling phenomenon in the marine environment. Despite massive maritime activities and a large industrial sector in the nearshore of the Laccadive Sea, studies describing pioneer bacterial colonizers and community succession during the early-stage biofilm are scarce. We investigated the biofilm-forming bacterial community succession on three substrata viz. stainless steel, high-density polyethylene, and titanium over 15 days of immersion in the seawater intake area of a power plant, located in the southern coastal region of India. The bacterial community composition of biofilms and peripheral seawater were analyzed by Illumina MiSeq sequenced 16S rRNA gene amplicons. The obtained metataxonomic results indicated a profound influence of temporal succession over substrate type on the early-stage biofilm-forming microbiota. Bacterial communities showed vivid temporal dynamics that involved variations in abundant bacterial groups. The proportion of dominant phyla viz. Proteobacteria decreased over biofilm succession days, while Bacteroidetes increased, suggesting their role as initial and late colonizers, respectively. A rapid fluctuation in the proportion of two bacterial orders viz. Alteromonadales and Vibrionales were observed throughout the successional stages. LEfSe analysis identified specific bacterial groups at all stages of biofilm development, whereas no substrata type-specific groups were observed. Furthermore, the results of PCoA and UPGMA hierarchical clustering demonstrated that the biofilm-forming community varied considerably from the planktonic community. Phylum Proteobacteria preponderated the biofilm-forming community, while the Bacteroidetes, Cyanobacteria, and Actinobacteria dominated the planktonic community. Overall, our results refute the common assumption that substrate material has a decisive impact on biofilm formation; rather, it portrayed that the temporal succession overshadowed the influence of the substrate material. Our findings provide a scientific understanding of the factors shaping initial biofilm development in the marine environment and will help in designing efficient site-specific anti-biofouling strategies.

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Bacterial Community Structure, Function and Diversity in Antarctic Sea Ice

10.26686/wgtn.16992562.v1 ◽

2021 ◽

Author(s):

◽

Rebecca Olivia MacLennan Cowie

Keyword(s):

Community Structure ◽

Bacterial Community ◽

Sea Ice ◽

Structure Function ◽

Bacterial Communities ◽

Bacterial Community Structure ◽

Ice Thickness ◽

Sea Ice Thickness ◽

Antarctic Sea Ice ◽

The Antarctic

<p>Antarctic sea ice is an important feature of the southern ocean where at its maximum it can cover 8 % of the Southern Hemisphere. It provides a stable environment for the colonisation of diverse and highly specialised microbes which play a central role in the assimilation and regulation of energy through the Antarctic food web. Polar environments are sensitive to changes in the environment. Small changes in temperature can have large effects on sea ice thickness and extent and Antarctic sea ice cover is expected to shrink by 25 % over the next century. It is unknown how the sea ice microbiota will respond. In order to understand the effects of climate change on the sea ice ecosystem it is necessary to obtain information about the community structure, function and diversity and their reactions with the environment. Studies have focused on algal diversity and physiology in Antarctic sea ice and in comparison studies on the prokaryotic community are few. Although prokaryotic diversity has been investigated using clone libraries and culture based methods, it is likely that certain species have still not been described. Almost nothing is known about the Antarctic sea ice bacterial community spatial and temporal dynamics under changing abiotic and biotic conditions or their role in biogeochemical cycles. This is the first study linking Antarctic bacterial communities to function by using statistics to investigate the relationships between environmental variables and community structure. Bacterial community structure was investigated by extracting both the DNA and RNA from the environment to understand both the metabolically active (RNA) and total (DNA) bacterial community. The thickness of the sea ice and nutrient concentrations were key factors regulating bacterial community composition in Antarctic sea ice. Sea ice thickness is likely to have an effect on the physiological responses of algae leading to changes in photosynthate concentrations and composition of dissolved organic matter (DOM). Further investigations into the relationships between enzymatic activity and community structure revealed that the composition of the DOM drove variation between bacterial communities. There was no relationship between bacterial abundance and chlorophyll-a (as a measure of algal biomass), suggesting a un-coupling of the microbial loop. However bacteria were actively involved in the hydrolysis of polymers throughout the sea ice core. Investigations using quantitative PCR (qPCR) found that the functional genes involved in denitrification and light energy utilisation were in low abundance therefore these processes are minor in Antarctic sea ice. These results confirm that sea ice bacteria are predominantly heterotrophs and have a major role in the cycling of carbon and nitrogen through the microbial loop ...</p>

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