Bacterial Communities of Lamiacea L. Medicinal Plants: Structural Features and Rhizosphere Effect.

Bacterial communities associated with medicinal plants are an essential part of ecosystems. The rhizosphere effect is rather important in the cultivation process. The purpose of the study was to analyze the rhizosphere effect of oregano (Origanum vulgare L.), peppermint (Mentha piperita L.), thyme (Thymus vulgaris L.), creeping thyme (Thymus serpillum L.) and sage (Salvia officinalis L.). To estimate the quantity of 16S bacteria ribosomal genes, qPCR assays were used. To compare bacterial communities' structure of medicinal plants rhizosphere with bulk soil high-throughput sequencing of the 16S rRNA targeting variable regions V3-V4 of bacteria was carried out. The highest bacterial abundance was associated with T. vulgaris L., M. piperita L. and S. officinalis L., and the lowest was associated with the O. vulgare L. rhizosphere. Phylum Actinobacteriota was predominant in all rhizosphere samples. The maximum bacterial α-diversity was found in S. officinalis L. rhizosphere. According to bacterial ß-diversity calculated by the Bray-Curtis metric, T. vulgaris L. root zone significantly differed from bulk soil. The rhizosphere effect was positive to the Myxococcota, Bacteroidota, Verrucomicrobiota, Proteobacteria and Gemmatimonadota.

Linking ecology and systematics of acidobacteria: Distinct habitat preferences of the Acidobacteriia and Blastocatellia in tundra soils.

The Acidobacteria is one of the major bacterial phyla in soils and peatlands. The currently explored diversity within this phylum is assigned to 15 class-level units, five of which contain described members. The ecologically relevant traits of acidobacteria from different classes remain poorly understood. Here, we compared the patterns of acidobacterial diversity in sandy soils of tundra, along a gradient of increasing vegetation-unfixed aeolian sand, semi-fixed surfaces with mosses and lichens, and mature soil under fully developed plant cover. The Acidobacteria-affiliated 16S rRNA gene sequences retrieved from these soils comprised 11 to 33% of total bacterial reads and belonged mostly to members of the classes Acidobacteriia and Blastocatellia, which displayed opposite habitat preferences. The relative abundance of the Blastocatellia was maximal in unfixed sands and declined in soils of vegetated plots, showing positive correlation with soil pH and negative correlation with carbon and nitrogen availability. An opposite tendency was characteristic for the Acidobacteriia. Most Blastocatellia-affiliated reads belonged to as-yet-undescribed members of the family Arenimicrobiaceae, which appears to be characteristic for dry, depleted in organic matter soil habitats. The pool of Acidobacteriia-affiliated sequences, apart from Acidobacteriaceae- and Bryobacteraceae-related reads, had a large proportion of sequences from as-yet-undescribed families, which seem to specialize in degrading plant-derived organic matter. This analysis reveals sandy soils of tundra as a source of novel acidobacterial diversity and provides an insight into the ecological preferences of different taxonomic groups within this phylum.