Bacterial community of cushion plant Thylacospermum ceaspitosum on elevational gradient in the Himalayan cold desert.

Klára Řeháková,Václav Krištůfek,Jiří Doležal,Josef Scharfen,Petr Čapek,Alica Chroňáková,Barbora Kuchtová,Kateřina Čapková

doi:10.3389/fmicb.2015.00304

Abstract

Although bacterial assemblages are important components of soils in arid ecosystems, the knowledge about composition, life-strategies, and environmental drivers is still fragmentary, especially in remote high-elevation mountains. We compared the quality and quantity of heterotrophic bacterial assemblages between the rhizosphere of the dominant cushion-forming plant Thylacospermum ceaspitosum and its surrounding bulk soil in two mountain ranges (East Karakoram: 4850–5250 m and Little Tibet: 5350–5850 m), in communities from cold steppes to the subnival zone in Ladakh, arid Trans-Himalaya, northwest India. Bacterial communities were characterized by molecular fingerprinting in combination with culture-dependent methods. The effects of environmental factors (elevation, mountain range, and soil physico-chemical parameters) on the bacterial community composition and structure were tested by multivariate redundancy analysis and conditional inference trees. Actinobacteria dominate the cultivable part of community and represent a major bacterial lineage of cold desert soils. The most abundant genera were Streptomyces, Arthrobacter, and Paenibacillus, representing both r- and K-strategists. The soil texture is the most important factor for the community structure and the total bacteria counts. Less abundant and diverse assemblages are found in East Karakoram with coarser soils derived from leucogranite bedrock, while more diverse assemblages in Little Tibet are associated with finer soils derived from easily weathering gneisses. Cushion rhizosphere is in general less diverse than bulk soil, and contains more r-strategists. K-strategists are more associated with the extremes of the gradient, with drought at lowest elevations (4850–5000 m) and frost at the highest elevations (5750–5850 m). The present study illuminates the composition of soil bacterial assemblages in relation to the cushion plant T. ceaspitosum in a xeric environment and brings important information about heterotrophic bacteria in Himalayan soil.

Highlights

Bacteria are a common and fundamental part of microbial communities and constitute a major proportion of biodiversity in soil ecosystems (Gans et al, 2005; Roesch et al, 2007; Fulthorpe et al, 2008; Griffiths et al, 2011)
Elevational gradients in mountains serve as powerful study systems for answering questions on how the functional diversity and biomass of bacteria can be affected by different microclimatic conditions provided by these gradients
The Response of the Bacterial Assemblages to Environmental Factors The combined effect of elevation, cushion habitat, and soil physico-chemical parameters on composition of bacterial assemblages derived from Capillary Electrophoresis Single Strand Conformation Polymorphism (CE-SSCP) profiles explained 55.2% of the total data variation in Nubra, which was highly significant

Summary

Introduction

Bacteria are a common and fundamental part of microbial communities and constitute a major proportion of biodiversity in soil ecosystems (Gans et al, 2005; Roesch et al, 2007; Fulthorpe et al, 2008; Griffiths et al, 2011). The first is that microbial populations can exhibit a geographic distribution (e.g., Fierer and Jackson, 2006; Adler et al, 2007; Griffiths et al, 2011). To eliminate the influence of plant composition, bacteria in the bulk soil in close vicinity and from rhizosphere of Thylacospermum caespitosum were studied. This is the dominant plant of nival and subnival zones of Trans-Himalaya Mountains

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