The Variability of the Predominant Culturable Plant Growth-Promoting Rhizobacterial Diversity in the Acidic Tea Rhizosphere Soils in the Eastern Black Sea Region

Abstract

The purpose of this study was to investigate the diversity of cultivable nitrogen fixing, phosphate solubilising and total bacteria originated from 580 rhizospheric acidic soils samples of tea plants grown at 62 locations. Based on FAME profiles of over 1428 rhizoplane bacteria, 63 bacterial genera were identified with a similarity index > 0.3, but 56.4% of the identified isolates belonged to six genera: Bacillus (37.02%), Pseudomonas (12.67%), Stenotrophomonas (5.71%), Paenibacillus (6.58%), Arthrobacter (4.35%) and Brevibacillus (3.98%). Most of the total, N2-fixing and P-solubilizing bacteria isolated were Gram positive (59.9, 58.8 and 56.3%) and Gram negative constituted only 40.1, 41.2 and 43.7%. Among different groups, Firmicutes, Gammaproteobacteria and Actinobacteria comprised the largest groups contributing to about 50.3 and 46.6%, 30.8 and 32.5%, and 8.3 and 9.6% of the total N2-fixing and P-solubilizing isolates, respectively. B. cereus, P. fluorescens, B. megaterium, S. maltophilia, P. putida, B. licheniformis, B. pumilus, B. subtilis and P. polymyxa were the most frequent N2-fixing and P-solubilizing species in the acidic tea rhizosohere soils. In these studies were evaluated to represent the dominant culturable diversity of diazotrophs and phosphobacteria, and thus potentially beneficial to the growth and survival of tea plants in that specific acidic ecosystem of eastern Black Sea region.

Isolation and in vitro screening of Pink Pigmented Facultative Methylobacterium (PPFMs) isolates for the production of phytohormones and ACC deaminase activity from the tea plantations of South India

“…However, only a few reports are available focusing on the PPFMs in the tea ecosystem. Chinese researchers, Xie et al, (2020) and Cakmakci (2019) reported the isolation a p p r o a c h e s a n d t h e d i s t r i b u t i o n o f Methylobacterium in the acidic tea rhizosphere soil. In North India, Bora et al, (2021)…”

A Review on Rhizosphere Microbiota of Tea Plant (Camellia sinensis L): Recent Insights and Future Perspectives

“…Further research shows that tea rhizosphere bacterial communities are often enriched with members of Proteobacteria , Firmicutes , and Acidobacteria , accounting for 67.81% of total rhizosphere bacteria. At the same time, Proteobacteria , Acidobacteria , and Chloroflexi were the main phyla in the tea bulk soil and accounted for 60.00% of total bulk soil bacteria (Figure a). − Nevertheless, the most abundant bacterial phyla in the tea rhizosphere soil were Firmicutes (with Bacillus and Lysinibacillus genera representing over 82.00%), which was about 2-fold or higher in the relative abundance in the tea rhizosphere soil (24.06%) than that in the bulk soil (9.31%). − Simultaneously, Verrucomicrobia was more abundant in the tea rhizosphere soil (5.34%) than in the bulk tea soil (2.73%). In contrast, Chloroflexi was enriched in the bulk soil (accounting for 11.05%), which was more than one-fold abundance in the bulk soil compared with that in the tea rhizosphere soil.…”

“…136 Besides, the rhizosphere bacteria belonging to genera Bacillus, Pseudomonas, Stenotrophomonas, Arthrobacter, and Serratia were the most frequent N-fixing bacteria in the tea rhizosphere soils. 25,137,138 Notably, for tea productivity, Azosprillum is the most efficient for increasing the N nutrient enhancement, which stimulates the density and length of tea plant root hairs through fixed nitrogen to absorb nutrition and increases tea plant biomass and survival rate. 139 Rhizosphere microorganisms can collectively maintain the content of soil-absorbable nitrogen compounds and improve the yield of tea plants by participating in nitrogen fixation.…”

“…It has been shown that the tea plants’ phosphorus solubilization mechanisms by producing organic acids or phosphatases to liberate phosphate achieved mineralization/solubilization from inorganic and organic phosphorus . For example, strains from the tea plant rhizosphere of bacterial genera Pseudomonas , Bacillus , and Enterobacter along with Aspergillus fungi are the most potent P-solubilizers causing local acidification and solubilizing soil mineral phosphate by the production of organic acids such as gluconic acid, oxalic acid, and malic acid. ,,,,, Additionally, a large diversity of rhizosphere microorganisms in tea plants (e.g., Serratia marcescens , Bacillus megaterium , and Bacillus aryabhattai ) are also able to mineralize the insoluble phosphate and make it available for the tea plant by the excretion of extracellular enzymes such as alkaline phosphatases, acid phosphatases, phytases, and C–P lyases . Of note, these two mechanisms (solubilization and mineralization) can coexist within the same PBKs .…”