Soil Salinity Controls Relative Abundance of Specific Bacterial Groups Involved in the Decomposition of Maize Plant Residues

Abstract

Extreme salinity and alkalinity in soil is known to inhibit organic material decomposition and affect the bacterial community structure involved in its mineralization. Regular flooding of these soils will reduce salinity, which will alter the bacterial community involved in organic material mineralization. Soil of the former lake Texcoco with electrolytic conductivity (EC) 157.4 dS m −1 and pH 10.3 was flooded monthly, amended with maize plant residue or its neutral detergent fiber [NDF; mostly (hemi)cellulose and some lignin], while C mineralization and the bacterial community structure was monitored by means of 454 pyrosequencing of the 16S rRNA gene. The EC of the soil dropped from 157.8 to 1.7 dS m −1 , but the pH (10.3) did not change significantly over time. On the one hand, the relative abundance of some bacterial groups, e.g., Bacillus and Gammaproteobacteria, always increased when maize plants or NDF were applied to soil independent of the changes in soil characteristics, i.e., they always participated in the degradation of the organic material applied, while the relative abundance of other groups, e.g., Acidobacteria, Alphaproteobacteria, Chloroflexi, Clostridia, Deltaproteobacteria, Gemmatimonadetes, Planctomycetes, and Verrucomicrobia, always decreased compared to the unamended soil. On the other hand, the increase or decrease of the relative abundance of other bacterial groups when organic material was applied to soil was influenced by the changes in soil characteristics. For instance, the relative abundance of the Actinomycetales, Halomonas, and Prauseria, did not increase when organic material was applied to soil with a high salt content, but did when the salt content was lowered while that of the Betaproteobacteria and Pirellulales increased when the salt content was high, but not when it was lowered. Application of the NDF generally had a similar effect on the bacterial community structure as when maize plants were applied. It was found that the capacity of some bacterial groups to degrade organic material was not affected by soil salt content, while that of others was stimulated or suppressed.

Mine reclamation using biofuel crops: Insights into the microbial ecology of the switchgrass (Panicum virgatum) microbiome

“…In contrast, Hobet's reclamation technique involved the application of crushed overburden with no topsoil amendment; thus I expected to observe a greater abundance of oligotrophic taxa, or taxa that thrive under low C conditions (Ishida and Kadota 1981;Kuznetsov et al 1979). Again, similar to my expectations, abundances of Actinobacteria, Alphaproteobacteria, and Chloroflexi, all of which are considered oligotrophic taxa (Fierer et al 2007;Ho et al 2017;De León-Lorenzana et al 2018;Mueller et al 2015), were of greater abundance in Hobet as compared to Hampshire. These results suggest that each sites' soil microbiome is selected for based upon the sites nutrient availability and the propensity of microbial taxa to exploit available nutrients.…”

“…Similar to the results observed in Chapter 1, reclamation strategy selected for a unique soil microbiome across sites, likely due to differences in nutrient availability. Similar site-specific trends existed, where Hampshire harbored generally greater relative abundances of Bacteroidetes, Betaproteobacteria, and Firmicutes, all of which are copiotrophic bacteria that preferentially degrade labile C compounds (Fierer et al 2007;Ho et al 2017;De León-Lorenzana et al 2018;Mueller et al 2015). Additionally, Hobet harbored generally greater relative abundances of Alphaproteobacteria and Chloroflexi, all of which are oligotrophic bacteria that typically degrade recalcitrant C substances (Ishida and Kadota 1981;Kuznetsov, Dubinina, and Lapteva 1979).…”

“…I expected a greater abundance of copiotrophic microbial taxa, or taxa that thrive in environments with readily-available C compounds (Fierer et al 2007) within Hampshire due to the increased amount of soil C and N compared to Hobet. Indeed, greater abundances of the bacterial phyla Bacteroidetes, Betaproteobacteria, and Firmicutes, all of which are typically considered copiotrophic due to their nutrient acquisition strategies (Fierer et al 2007;Ho et al 2017;De León-Lorenzana et al 2018;Mueller, Belnap, and Kuske 2015) were observed at Hampshire compared to Hobet. In contrast, Hobet's reclamation technique involved the application of crushed overburden with no topsoil amendment; thus I expected to observe a greater abundance of oligotrophic taxa, or taxa that thrive under low C conditions (Ishida and Kadota 1981;Kuznetsov et al 1979).…”

Research Advances of Beneficial Microbiota Associated with Crop Plants

“…In addition, plants need soil microbiota for degrading their residues [124]. Plant residues are abundantly found in the soil [124,125]. Although chemical or physical methods can help degrade the residues, the natural degradation is carried out by soil microbes [125].…”

“…Plant residues are abundantly found in the soil [124,125]. Although chemical or physical methods can help degrade the residues, the natural degradation is carried out by soil microbes [125]. The microbiota assembles and is enriched in the plant residues and further degrades them into macro-or micromolecules, which can serve as soil organic matter [125].…”