Bacterial diversity in the rhizosphere of maize and the surrounding carbonate‐rich bulk soil

Abstract

Maize represents one of the main cultivar for food and energy and crop yields are influenced by soil physicochemical and climatic conditions. To study how maize plants influence soil microbes we have examined microbial communities that colonize maize plants grown in carbonate-rich soil (pH 8.5) using culture-independent, PCR-based methods. We observed a low proportion of unclassified bacteria in this soil whether it was planted or unplanted. Our results indicate that a higher complexity of the bacterial community is present in bulk soil with microbes from nine phyla, while in the rhizosphere microbes from only six phyla were found. The predominant microbes in bulk soil were bacteria of the phyla Acidobacteria, Bacteroidetes and Proteobacteria, while Gammaproteobacteria of the genera Pseudomonas and Lysobacter were the predominant in the rhizosphere. As Gammaproteobacteria respond chemotactically to exudates and are efficient in the utilization of plants exudate products, microbial communities associated to the rhizosphere seem to be plant-driven. It should be noted that Gammaproteobacteria made available inorganic nutrients to the plants favouring plant growth and then the benefit of the interaction is common.

Rhizosphere bacteriome of the medicinal plant Sapindus saponaria L. revealed by pyrosequencing

“…Chao1 estimator value for S. saponaria rhizosphere was 10,790.46. The Shannon and Simpson indexes were 7.237 and 0.0027, respectively, for the Sapindus rhizosphere (present work) and 3.42 and 0.059, respectively, for maize rhizosphere (García-Salamanca et al, 2013), indicating that the bacterial community in the S. saponaria rhizosphere was more complex than the maize rhizosphere. Similar to the observations of García-Salamanca et al (2013), the most predominant 16S rRNA gene sequences in the S. saponaria rhizosphere were those of Actinobacteria, Acidobacteria, and Proteobacteria.…”

“…The soil microbial biomass carbon and nitrogen, and nitrification, are also significantly positively correlated to the soil pH (Kemmitt et al, 2006). The index values for the 2660 OTUs of S. saponaria rhizosphere, at 3% distance sequence dissimilarity, were much higher than the values obtained by García-Salamanca et al (2013), who studied the bacterial diversity of maize rhizosphere. They obtained less than 60 OTUs from a relatively high pH, carbonate-rich soil typical of Southern Spain.…”

“…We also analyzed the chemical composition of the soil to investigate whether environmental factors, such as macro-and micro-nutrients or pH, could explain bacterial richness in the rhizosphere. According to García-Salamanca et al (2013), the taxonomical and functional structures of soil microbial communities are influenced by biotic and abiotic factors, including the physicochemical characteristics of the soil and presence of plants. The authors pointed out that plants exert selective pressure on the soil microbial population through modification of the physicochemical characteristics of the surrounding soil and by the excretion of exudates consisting of amino acids, organic acids, proteins, and other chemicals that act as chemoattractants or chemorepellents.…”

Dynamics of the bacterial community structure in the rhizosphere of a maize cultivar

“…SI_7). Another study conducted in the carbonate-rich soil (pH 8.5) using 16S rRNA clone library analysis showed that Pseudomonas and Lysobacter genera constituted 45% of the total bacterial abundance in the maize rhizosphere (García-Salamanca et al, 2013). Though exact mechanisms for such differences are not completely understood, because these studies were all conducted on different soil types, it is likely that soil type may be one of the most important environmental variables influencing the structure of the maize root-inhabiting bacterial community at low taxonomic levels (Berg and Smalla, 2009;Castellanos et al, 2009;Garbeva et al, 2004).…”

Metagenome of Amazon forest conversion: impacts on soil-borne microbial diversity and functions

“…Gammaproteobacteria, which was abundant in rhizosphere samples, and respond chemotactically to exudates and are efficient in the utilization of plants exudate products (GARCÍA-SALAMANCA et al, 2012). The class Alphaproteobacteria presented a significant enrichment in the 5-year soybean rhizosphere.…”