Acta Microbiologica et Immunologica Hungarica, 61 (3), pp. 347–361 (2014) DOI: 10.1556/AMicr.61.2014.3.8

METABOLIC ACTIVITY AND GENETIC DIVERSITY OF MICROBIAL COMMUNITIES INHABITING THE RHIZOSPHERE OF HALOPHYTON PLANTS ÁGNES BÁRÁNY1, TIBOR SZILI-KOVÁCS2, GERGELY KRETT1, ANNA FÜZY2, KÁROLY MÁRIALIGETI1 and ANDREA K. BORSODI1* 1

Department of Microbiology, Eötvös Loránd University, Pázmány P. sétány 1/C, H-1117 Budapest, Hungary 2 Institute for Soil Sciences and Agricultural Chemistry, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó út 15, H-1022 Budapest, Hungary

(Received: 9 May 2014; accepted: 26 June 2014)

A preliminary study was conducted to compare the community level physiological profile (CLPP) and genetic diversity of rhizosphere microbial communities of four plant species growing nearby Kiskunság soda ponds, namely Böddi-szék, Kelemen-szék and Zab-szék. CLPP was assessed by MicroResp method using 15 different substrates while Denaturing Gradient Gel Electrophoresis (DGGE) was used to analyse genetic diversity of bacterial communities. The soil physical and chemical properties were quite different at the three sampling sites. Multivariate statistics (PCA and UPGMA) revealed that Zab-szék samples could be separated according to their genetic profile from the two others which might be attributed to the geographical location and perhaps the differences in soil physical properties. Böddi-szék samples could be separated from the two others considering the metabolic activity which could be explained by their high salt and low humus contents. The number of bands in DGGE gels was related to the metabolic activity, and positively correlated with soil humus content, but negatively with soil salt content. The main finding was that geographical location, soil physical and chemical properties and the type of vegetation were all important factors influencing the metabolic activity and genetic diversity of rhizosphere microbial communities. Keywords: soda soil, rhizosphere bacterial communities, DGGE, MicroResp, SIR

* Corresponding author; E-mail: [email protected]

1217-8950/$20.00 © 2014 Akadémiai Kiadó, Budapest

348

BÁRÁNY et al.

Introduction Soda ponds formed naturally at several locations in the Great Hungarian Plain within the Carpathian Basin are flooded periodically, and their water can be characterized with high carbonate content and high pH values [1]. In the neighbouring areas of these ponds, soda and saline-soda soils are formed due to the high salt content of groundwater near the surface. Soda soils belonging to the hydromorphic type are influenced by the groundwater as the most important soil developing factor [2]. Vegetation around soda ponds is typically arranged into zones which can be classified based on the duration of inundation during the year. Distribution of the macrovegetation types correlates closely with the salt concentration near the soil surface [3]. Closest to the soda ponds, salt marshes can be found which are covered by saline water in the major part of the vegetation period (occasionally year-round). Here, the Bolboschoeno–Phragmitetum plant association is typical. Further away from the ponds, this community is replaced by dense and tall Puccinellia swards (so-called “szikfok” in Hungarian) which usually experience flooding for a long period during the year (wet in springtime but sometimes completely dry in summer). At even greater distance from the soda ponds, mesotrophic wet meadows are typical which are mesic during most part of the vegetation period (often have spring water cover but dries out in summer). These are followed by salt meadows which undergo seasonal inundation at the beginning of the vegetation period [4]. In soda ponds, high temperature, intensive sun radiation and the high number of sunny hours are responsible for the high primary production of photosynthetic prokaryotes [5, 6]. Alkaliphilic and alkalitolerant chemoorganotrophic bacterial communities are based on this primary production [1]. Microorganisms living in soda ponds and soils can adapt to the variable and extreme environmental conditions [7]. These organisms not only tolerate the alkaline and saline habitats, rather depend on it. Soil microbial activity and biomass are negatively affected by salinity. The microbial biomass in saline soils appears to be limited primarily by substrate availability and only secondarily by salinity [9]. Some studies found that the bacteria–fungi ratio increased with increasing osmotic potential, due to a greater sensitivity of fungi to salinity compared to bacteria [10]. Nowadays, several studies have been performed to get insight into the composition and activities of bacterial communities adapted to the extremities of Hungarian soda ponds [11–13], however, little or no information is available about the

Acta Microbiologica et Immunologica Hungarica 61, 2014

MICROBIAL COMMUNITIES INHABITING THE RHIZOSPHERE OF HALOPHYTON PLANTS

349

bacterial communities inhabiting the rhizosphere of plants living in the different macrovegetation zones near these soda ponds. Therefore, the aim of this study was to reveal and compare the genotypic diversity and metabolic activity of microbial communities inhabiting the rhizosphere of different halophyton plant species living in the adjacent area of soda ponds located in Kiskunság National Park (KNP).

Materials and Methods Study sites and samplings Approximately 500–500 g of rhizosphere samples of some typical halophyton plant species were collected into sterile jars near Böddi-szék, Kelemenszék and Zab-szék soda ponds located in Kiskunság National Park in September 2013 (Table I). Samples were kept cool (6–8°C) until laboratory processing within 24 hours. Prior to the laboratory tests, roots and other visible plant residues were removed using a 2 mm mesh sieve. The most important physical and chemical parameters of the samples measured are presented in Table II. Soil chemical analyses were performed from air-dried, sieved (mesh size

Metabolic activity and genetic diversity of microbial communities inhabiting the rhizosphere of halophyton plants.

A preliminary study was conducted to compare the community level physiological profile (CLPP) and genetic diversity of rhizosphere microbial communiti...
160KB Sizes 0 Downloads 9 Views