Leguminosae native nodulating bacteria from a gold mine As-contaminated soil: Multi-resistance to trace elements, and possible role in plant growth and mineral nutrition

Abstract

Efficient N-fixing Leguminosae nodulating bacteria resistant to As may facilitate plant growth on As-contaminated sites. In order to identify bacteria holding these features, 24 strains were isolated from nodules of the trap species Crotalaria spectabilis (12) and Stizolobium aterrimum (12) growing on an As-contaminated gold mine site. 16S rRNA gene sequencing revealed that most of the strains belonged to the group of α-Proteobacteria, being representatives of the genera Bradyrhizobium, Rhizobium, Inquilinus, Labrys, Bosea, Starkeya, and Methylobacterium. Strains of the first four genera showed symbiotic efficiency with their original host, and demonstrated in vitro specific plant-growth-promoting (PGP) traits (production of organic acids, indole-3-acetic-acid and siderophores, 1-aminocyclopropane-1-carboxylate deaminase activity, and Ca(PO) solubilization), and increased resistance to As, Zn, and Cd. In addition, these strains and some type and reference rhizobia strains exhibited a wide resistance spectrum to β-lactam antibiotics. Both intrinsic PGP abilities and multi-element resistance of rhizobia are promising for exploiting the symbiosis with different legume plants on trace-element-contaminated soils.

Characterization of Gene Families Encoding Beta-Lactamases of Gram-Negative Rods Isolated from Ready-to-Eat Vegetables in Mexico City

“…These data show—by the Kirby–Bauer method—that the isolated Enterobacteriaceae have a multi-resistance pattern to beta-lactam antibiotics, including penicillins and cephalosporins, and even were resistant to beta-lactamase inhibitors. These results are in agreement with work done on nitrogen-fixing legumes, where the pattern of multi-resistance was evaluated by a disk diffusion method for β-lactam antibiotics, with reported resistance to Amoxicillin, Ampicillin, Cefadroxil, Ceftriaxone, Oxacillin, and Vancomycin [43]. The food contamination of ready-to-eat salads distributed freely in Mexico City has the potential to become a trigger vector of an epidemic of gastrointestinal infection that is caused by multi-resistant Enterobacteriaceae, which could compromise the lives of patients at risk by their difficult treatment.…”

Streptomyces lydicus M01 Regulates Soil Microbial Community and Alleviates Foliar Disease Caused by Alternaria alternata on Cucumbers

“…Most of the bacteria from the genera listed above have characteristics associated with pathogen inhibition, plant auxin biosynthesis or bioremediation. However, the abundance of Bradyrhizobium and Pseudolabrys that both function in nitrogen fixation (Hennecke, 1990;Rangel et al, 2017;Wongdee et al, 2018) were significantly reduced. Furthermore, the abundance of Limnobacter species that have the ability to oxidize thiosulfate (Lu et al, 2011;Vedler et al, 2013) was also reduced.…”

Streptomyces lydicus A01 affects soil microbial diversity, improving growth and resilience in tomato

“…All of the bacteria from the genera or species listed above (identified by the sequences of OTU686, OTU509, OTU1256, OTU515, OTU346, OTU442, OTU314, OTU318 and OTU508) have characteristics related to nutrient accumulation, plant auxin biosynthesis, pathogen inhibition, and bioremediation, and were significantly increased in the presence of S. lydicus A01. However, the abundance of Pseudolabrys (OTU848), a Rhizobiales from Alphaproteobacteria that functions in nitrogen fixation (Noel et al ; Cheng ; Kim et al ; Rangel et al ) was significantly reduced following S. lydicus A01 treatment. Furthermore, the levels of several proteobacterial strains (OTU683, OTU210 and OTU1129) were reduced.…”