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Analysing biogeographical diversity of plant associated bacterial communities from soil in European arctic tunra

Kumar, Manoj (2012) MOBN18 20111
Degree Projects in Molecular Biology
Abstract
BIOGEOGRAPHICAL DIVERSITY OF PLANT ASSOCIATED BACTERIAL COMMUNITIES ARCTIC TUNDRA

Global warming is predicted to affect the Polar Regions most rapidly due to glacial retreat, snow cover reduction, melting of ice sheets and thawing of permafrost soils. Increase in temperature will further influence the native species to shift northerly by invasive pressure of species well adapted to warm temperatures. Whereas the plants with the northern limits may move further north along the retreating glaciers and or perhaps go extinct due to poor dispersal pattern. Survival of the Arctic plant species are coupled with bacterial endophytes due to the harsh environmental stress (UV rays, continuous light and darkness) and nutrient limitation.

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BIOGEOGRAPHICAL DIVERSITY OF PLANT ASSOCIATED BACTERIAL COMMUNITIES ARCTIC TUNDRA

Global warming is predicted to affect the Polar Regions most rapidly due to glacial retreat, snow cover reduction, melting of ice sheets and thawing of permafrost soils. Increase in temperature will further influence the native species to shift northerly by invasive pressure of species well adapted to warm temperatures. Whereas the plants with the northern limits may move further north along the retreating glaciers and or perhaps go extinct due to poor dispersal pattern. Survival of the Arctic plant species are coupled with bacterial endophytes due to the harsh environmental stress (UV rays, continuous light and darkness) and nutrient limitation.

Several studies have shown that plants have a tendency to select its own microbial community from soil via root by synthesizing unique signaling molecules. These communities differ based upon the plant species, its physiology and even among different plant parts. Plants do have the tendency to create specific ecological niche that in turn selects certain bacterial species or groups. However, their ecology, origin, functioning, selection, and properties were not studied in detail.

In this I studied the influence of plants in the diversity of soil bacterial community based on two distinct geographic regions Kilpisjärvi, Finland (Sub-Arctic) and Svalbard, Norway (high-Arctic). As Arctic plants experience extreme stress and we hypothesize that plant-bacterial interactions will be a key factor in their survival strategy. Our previous studies have shown that a portion of endophytic bacteria of Oxyria digyna are host specific and even inoculated in its seeds. Subsequently, a more comprehensive study on plant-associated soil bacterial community was carried out for a detailed understanding. Terminal restriction fragment analysis (T-RFLP) and community profiling by BIOLOG GEN III Microplates were used to access the influence of plant species on bacterial community.

16S rRNA and nifH T-RFLP analyses indicated a difference in soil bacterial communities between two regions. Further, clustering analysis of rhizosphere samples explained the effect of vegetation on bacterial diversity; while similar bacterial community was detected between rhizosphere samples of O. digyna and Saxifraga opposit i folia. Interestingly, community profiling also indicated a comparable difference between geographical region and different plant species. Samples from Saana site also had distinct microbial community when compared with other sites from Kilpisjärvi and only difference being sampling of O. digyna alone. Even soi l background data was similar among the sites. These results indicate that even though there is a biogeographical diversity in microbial community, the differences in the vegetation type and plant species do influence bacterial community structure.

It is surprising to discover the bacterial diversity among rhizosphere samples of O. digyna and S. oppositifolia even though i t was sampled strikingly close. It summarizes that plants do regulate the soil characteristics and alters its physical chemical composition through its litters and handpick their bacterial relatives. Even though, influence of plant species was observed more data is needed to conclude any hypothesis. Variation in bacterial diversity of samples from Saana site is encouraging. The nifH diversity and the functional characteristics of nitrogen-fixers will be interesting to study based on O. digyna. Additionally we are also planning to pyrosequence our samples in future to analyse the endobacterial diversity and compare it with the soil data.

Supervisor: Dr. Riitta Nissinen
Master´s Degree Project - Microbiology, 45 credits
Department of Microbial Ecology
University of Groningen,
The Netherlands (Less)
Please use this url to cite or link to this publication:
author
Kumar, Manoj
supervisor
organization
course
MOBN18 20111
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
3633122
date added to LUP
2013-04-12 11:04:07
date last changed
2013-04-12 11:04:07
@misc{3633122,
  abstract     = {BIOGEOGRAPHICAL DIVERSITY OF PLANT ASSOCIATED BACTERIAL COMMUNITIES ARCTIC TUNDRA 

Global warming is predicted to affect the Polar Regions most rapidly due to glacial retreat, snow cover reduction, melting of ice sheets and thawing of permafrost soils. Increase in temperature will further influence the native species to shift northerly by invasive pressure of species well adapted to warm temperatures. Whereas the plants with the northern limits may move further north along the retreating glaciers and or perhaps go extinct due to poor dispersal pattern. Survival of the Arctic plant species are coupled with bacterial endophytes due to the harsh environmental stress (UV rays, continuous light and darkness) and nutrient limitation. 

Several studies have shown that plants have a tendency to select its own microbial community from soil via root by synthesizing unique signaling molecules. These communities differ based upon the plant species, its physiology and even among different plant parts. Plants do have the tendency to create specific ecological niche that in turn selects certain bacterial species or groups. However, their ecology, origin, functioning, selection, and properties were not studied in detail. 

In this I studied the influence of plants in the diversity of soil bacterial community based on two distinct geographic regions Kilpisjärvi, Finland (Sub-Arctic) and Svalbard, Norway (high-Arctic). As Arctic plants experience extreme stress and we hypothesize that plant-bacterial interactions will be a key factor in their survival strategy. Our previous studies have shown that a portion of endophytic bacteria of Oxyria digyna are host specific and even inoculated in its seeds. Subsequently, a more comprehensive study on plant-associated soil bacterial community was carried out for a detailed understanding. Terminal restriction fragment analysis (T-RFLP) and community profiling by BIOLOG GEN III Microplates were used to access the influence of plant species on bacterial community.

16S rRNA and nifH T-RFLP analyses indicated a difference in soil bacterial communities between two regions. Further, clustering analysis of rhizosphere samples explained the effect of vegetation on bacterial diversity; while similar bacterial community was detected between rhizosphere samples of O. digyna and Saxifraga opposit i folia. Interestingly, community profiling also indicated a comparable difference between geographical region and different plant species. Samples from Saana site also had distinct microbial community when compared with other sites from Kilpisjärvi and only difference being sampling of O. digyna alone. Even soi l background data was similar among the sites. These results indicate that even though there is a biogeographical diversity in microbial community, the differences in the vegetation type and plant species do influence bacterial community structure. 

It is surprising to discover the bacterial diversity among rhizosphere samples of O. digyna and S. oppositifolia even though i t was sampled strikingly close. It summarizes that plants do regulate the soil characteristics and alters its physical chemical composition through its litters and handpick their bacterial relatives. Even though, influence of plant species was observed more data is needed to conclude any hypothesis. Variation in bacterial diversity of samples from Saana site is encouraging. The nifH diversity and the functional characteristics of nitrogen-fixers will be interesting to study based on O. digyna. Additionally we are also planning to pyrosequence our samples in future to analyse the endobacterial diversity and compare it with the soil data.

Supervisor: Dr. Riitta Nissinen
Master´s Degree Project - Microbiology, 45 credits
Department of Microbial Ecology 
University of Groningen, 
The Netherlands},
  author       = {Kumar, Manoj},
  language     = {eng},
  note         = {Student Paper},
  title        = {Analysing biogeographical diversity of plant associated bacterial communities from soil in European arctic tunra},
  year         = {2012},
}