Copper tolerance in Frankia sp. strain EuI1c involves surface binding and copper transport

Abstract

Several Frankia strains have been shown to be copper-tolerant. The mechanism of their copper tolerance was investigated for Frankia sp. strain EuI1c. Copper binding was shown by binding studies. Unusual globular structures were observed on the surface of the bacterium. These globular structures were composed of aggregates containing many relatively smaller "leaf-like" structures. Scanning electron microscopy with energy-dispersive X-ray (SEM-EDAX) analysis of these structures indicated elevated copper and phosphate levels compared to the control cells. Fourier transform infrared spectroscopy (FTIR) analysis indicated an increase in extracellular phosphate on the cell surface of copper-stressed cells. Bioinformatics' analysis of the Frankia sp. strain EuI1c genome revealed five potential cop genes: copA, copZ, copC, copCD, and copD. Experiments with Frankia sp. strain EuI1c using qRT-PCR indicated an increase in messenger RNA (mRNA) levels of the five cop genes upon Cu(2+) stress. After 5 days of Cu(2+) stress, the copA, copZ, copC, copCD, and copD mRNA levels increased 25-, 8-, 18-, 18-, and 25-fold, respectively. The protein profile of Cu(2+)-stressed Frankia sp. strain EuI1c cells revealed the upregulation of a 36.7 kDa protein that was identified as FraEuI1c_1092 (sulfate-binding periplasmic transport protein). Homologues of this gene were only present in the genomes of the Cu(2+)-resistant Frankia strains (EuI1c, DC12, and CN3). These data indicate that copper tolerance by Frankia sp. strain EuI1c involved the binding of copper to the cell surface and transport proteins.

Real‐time PCR based analysis of metal resistance genes in metal resistant Pseudomonas aeruginosa strain J007

“…The present study showed that both the metal resistance genes were induced to various extents depending on metal concentration and time of exposure. Previous studies on different metal resistant bacterial strains have shown that genetic determinants for metal transporters belonging to RND family as well as Cu sequestration are induced in presence of elevated levels of heavy metal substrates [10,16,17,29,31,32]. Elevated expression of both copA and czcA genes in response to either of the test metals corroborated very well with a study on transcriptional network involved in metal homeostasis in metal resistant bacteria.…”

Bioremediation of Heavy Metals

“…These smaller structures were about 5 μm in diameter and were also observed as individual structures throughout the hyphae. At higher magnification, the structures have a grooved pattern and appear connected to the hyphae by amorphous material [21]. Similar globular structures were observed with SEM of other copper-resistant Frankia strains (e.g., strain DC12).…”

“…The cells grown in the elevated copper levels appeared blue which suggest that copper was accumulating inside of Frankia or binding to the cell surface [21]. When observed under phase-contrast microscopy, Cu +2 -resistant Frankia EuI1c formed unusual globular structures that were associated with their hyphae [20].…”

“…These results suggest that a copper-phosphate compound forms and binds to Frankia cell surface. The EDAX spectra showed that the bodies present in the cells were mainly composed of phosphorus and oxygen [8,21]. The highly sensitive MS analysis of excised bands produced peptides such as periplasmic binding protein/LacI transcriptional regula tor (E3IXA6; FraEuI1c_7040 gene) with the appropriate protein size (37.6 kDa).…”

Contamination of the Arctic reflected in microbial metagenomes from the Greenland ice sheet

“…The closest neighbor does not necessarily indicate the taxonomy of the query genome but indicates similarity in assigned functions between the query genome and the closest neighbor. cellular mechanisms for increased copper tolerance [41]. The closest neighbor of bin 47, Caulobacter sp.…”