Study of pandrug and heavy metal resistance among E. coli from anthropogenically influenced Delhi stretch of river Yamuna

Abstract Escalating burden of antibiotic resistance that has reached new heights present a grave concern to mankind. As the problem is no longer confined to clinics, we hereby report identification of a pandrug resistant Escherichia coli isolate from heavily polluted Delhi stretch of river Yamuna, India. E. coli MRC11 was found sensitive only to tobramycin against 21 antibiotics tested, with minimum inhibitory concentration values >256 µg/mL for amoxicillin, carbenicillin, aztreonam, ceftazidime and cefotaxime. Addition of certain heavy metals at higher concentrations were ineffective in increasing susceptibility of E. coli MRC11 to antibiotics. Withstanding sub-optimal concentration of cefotaxime (10 µg/mL) and mercuric chloride (2 µg/mL), and also resistance to their combinatorial use, indicates better adaptability in heavily polluted environment through clustering and expression of resistance genes. Interestingly, E. coli MRC11 harbours two different variants of blaTEM (blaTEM-116 and blaTEM-1 with and without extended-spectrum activity, respectively), in addition to mer operon (merB, merP and merT) genes. Studies employing conjugation, confirmed localization of blaTEM-116, merP and merT genes on the conjugative plasmid. Understanding potentialities of such isolates will help in determining risk factors attributing pandrug resistance and strengthening strategic development of new and effective antimicrobial agents.

Plant Growth Promotion and Root Colonization by EPS Producing Enterobacter sp. RZS5 under Heavy Metal Contaminated Soil.

The heavy metal resistant bacterium isolated from field soil and identified as Enterobacter sp. RZS5 tolerates a high concentration (100-2000 mM) of various heavy metal ions such as Mn2+, Ni2+, Zn2+, Cu2+, CO2+ and Fe2+ when grown in such environment and produces exopolysaccharides (EPS). Here, we have demonstrated EPS production by Enterobacter sp. RZS5 during 60 h of growth in yeast extract mannitol broth (YEMB). The yield increased by two fold after the addition of 60 M of Ca2+; 50 M of Fe2+ and 60 M of Mg2+ ions in YEMB, and the optimization of physico-chemical parameters. EPS was extracted with 30% (v/v) of isopropanol as against the commonly used 50% (v/v) isopropanol method. EPS-rich broth promoted seed germination, shoot height, root length, number of leaves and chlorophyll content of wheat (Triticum aestivum) and peanut (Arachis hypogaea) seeds. The higher colony-forming unit of Enterobacter sp. in soil inoculated with EPS rich broth of Enterobacter sp. indicated the root colonizing potential and rhizosphere competence of the isolate. The FTIR spectra of the EPS extract confirmed the presence of the functional group characteristics of EPS known to exhibit a high binding affinity towards certain metal ions. This overall growth and vigour in plants along with the effective root colonization, reflected the potential of the isolate as an efficient bio-inoculant in bioremediation.

Metagenomic analysis of cadmium and copper resistance genes in activated sludge of a tannery wastewater treatment plant.

In order to comprehensively characterize the copper and cadmium resistance in activated sludge of a tannery wastewater treatment plant, a resistance protein database of the two heavy metals was manually created by retrieving annotated sequences and related information from the public databases and published literatures. The metagenomic DNA was extracted from the activated sludge for Illumina high-throughput sequencing, and the obtained 11,973,394 clean reads (1.61 Gb) were compared against the established databases using BLAST tool. Annotations of the BLAST hits showed that 222 reads (0.019‰) and 197 reads (0.016‰) were identified as copper and cadmium resistance genes, respectively. Among the identified cadmium resistance genes, czcA encoding cobalt-zinc-cadmium resistance protein had the highest abundance (83 reads, 0.0069‰), which was further confirmed by annotation of the open reading frames predicted with the assembly contigs. Among the copper resistance genes, copA (66 reads, 0.0055‰) was most abundant, followed by copK and cusR. Alignment against the Clusters of Orthologous Groups (COG) database also suggested that 87.26% of the matched reads were grouped in COG0474 (cation transport ATPase). This study may be practically helpful for exploring various functional genes in the environment using high-throughput sequencing and bioinformatics methods.

Heavy Metal Resistance Strategies of Acidophilic Bacteria and Their Acquisition: Importance for Biomining and Bioremediation

Microbial solubilizing of metals in acid environments is successfully used in industrial bioleaching of ores or biomining to extract metals such as copper, gold, uranium and others. This is done mainly by acidophilic and other microorganisms that mobilize metals and generate acid mine drainage or AMD, causing serious environmental problems. However, bioremediation or removal of the toxic metals from contaminated soils can be achieved by using the specific properties of the acidophilic microorganisms interacting with these elements. These bacteria resist high levels of metals by using a few "canonical" systems such as active efflux or trapping of the metal ions by metal chaperones. Nonetheless, gene duplications, the presence of genomic islands, the existence of additional mechanisms such as passive instruments for pH and cation homeostasis in acidophiles and an inorganic polyphosphate-driven metal resistance mechanism have also been proposed. Horizontal gene transfer in environmental microorganisms present in natural ecosystems is considered to be an important mechanism in their adaptive evolution. This process is carried out by different mobile genetic elements, including genomic islands (GI), which increase the adaptability and versatility of the microorganism. This mini-review also describes the possible role of GIs in metal resistance of some environmental microorganisms of importance in biomining and bioremediation of metal polluted environments such as Thiomonas arsenitoxydans, a moderate acidophilic microorganism, Acidithiobacillus caldus and Acidithiobacillus ferrooxidans strains ATCC 23270 and ATCC 53993, all extreme acidophiles able to tolerate exceptionally high levels of heavy metals. Some of these bacteria contain variable numbers of GIs, most of which code for high numbers of genes related to metal resistance. In some cases there is an apparent correlation between the number of metal resistance genes and the metal tolerance of each of these microorganisms. It is expected that a detailed knowledge of the mechanisms that these environmental microorganisms use to adapt to their harsh niche will help to improve biomining and metal bioremediation in industrial processes.

Resistances of antibiotics and heavy metals in Enterobacteriaceae spp. isolated from gills and intestines of Achanthobrama marmid (Heckel,1843) from Sir Dam lake Turkey.

A total of 94 bacteria, associated with wild Achanthobrama marmid (Heckel, 1843) in Sir Dam lake of Turkey identified. Subsequently, selected isolates were characterized and identified to the genus level. The 94 members of Enterobacteriaceae were isolated in the gills and intestines, and among the isolates, E. coli were represented at a rate of 55 %, Shigella spp. at a rate of 21 %, Salmonella spp. at a rate of 9%, Citrobacter spp. at a rate of 9%, Klebsiella spp. at a rate of 3% and Proteus spp., at a rate of 3%. A total of 94 bacteria resistant to antibiotics and heavy metals were isolated from total 47 of A. marmid samples and were investigated. Viable counts of antibiotic resistant bacteria isolated from gill and intestinal content samples showed high frequencies of resistance to Penicilline-G (KP) (68%), CZ (54%), FOX (48%), while the proportion of CRO (39%) and CTX (36%) resistance was low. In this research, heavy metal contamination in Sir Dam lake water samples and resistance frequency against heavy metals in isolated bacteria from gill and intestinal contents in A. marmid were investigated. Heavy metal contamination such as nickel (Ni), cadmium (Cd), copper (Cu) and chromium (Cr) determined diverse rate (except Mn) in water samples. The resistance frequency of the isolates was revealed different rate for the following heavy metals: Ni, Cd, Cu and Cr. When the concentration of heavy metals increased, the resistance against heavy metals in diverse genus of isolates in different rate decreased.

Occurrence of heavy metals and antibiotic resistance in bacteria from internal organs of american bullfrog (Rana catesbeiana) raised in Malaysia

A total of 40 bacteria have been successfully isolated from internal organs of the American bullfrog (Rana catesbeiana) raised in Malaysia, namely, eight isolates of Aeromonas spp., 21 of Edwardsiella spp., six of Flavobacterium spp. and five of Vibrio spp. In terms of antibiotic susceptibility testing, each isolate was tested against 21 antibiotics, resulting in 482 (57.3 percent) cases of sensitivity and 61 (7.3 percent) cases of partial sensitivity. Meanwhile, 297 (35.4 percent) bacterial isolates were registered as resistant. The multiple antibiotic resistance (MAR) index of each bacterial species indicated that bacteria from raised bullfrogs have been exposed to tested antibiotics with results ranging from 0.27 to 0.39. Additionally, high percentages of heavy metal resistance among these isolates were observed, with values ranging from 85.0 to 100.0 percent. The current results provided us information on bacterial levels of locally farmed bullfrogs exposed to copper, cadmium, chromium as well as 21 types of antibiotics.(AU)

Heavy metal resistance of microorganisms isolated from coal mining environments of Santa Catarina

The coal mining activity is characterized by the generation of large amount of by-products. One of them is pyrite, which tends to acidify the water, solubilizing heavy metals. As a consequence the environment becomes acid and rich in heavy metals, selecting microorganisms able to survive in this condition, which are of great interest as bioremediation agents. This work describes the isolation and characterization of microorganisms from a coal mining area in Santa Catarina. These microorganisms comprised bacteria, fungi and yeasts resistant to zinc, nickel and cadmium.

A atividade de mineração do carvão é responsável pela geração de diferentes sub-produtos. Entre esses, está a pirita que acidifica a água e acelera o processo de solubilização de metais. Como conseqüência, o ambiente torna-se ácido e rico em metais pesados, os quais selecionam os microrganismos capazes de sobreviver nestas condições. Esses microrganismos podem, por sua vez, serem empregados como agentes para a biorremediação de áreas contaminadas com metais pesados. No presente trabalho é descrito o isolamento e a caracterização de bactérias, fungos e leveduras resistentes aos metais zinco, níquel e cádmio.

Heavy metal resistance of microorganisms isolated from coal mining environments of Santa Catarina

The coal mining activity is characterized by the generation of large amount of by-products. One of them is pyrite, which tends to acidify the water, solubilizing heavy metals. As a consequence the environment becomes acid and rich in heavy metals, selecting microorganisms able to survive in this condition, which are of great interest as bioremediation agents. This work describes the isolation and characterization of microorganisms from a coal mining area in Santa Catarina. These microorganisms comprised bacteria, fungi and yeasts resistant to zinc, nickel and cadmium.

A atividade de mineração do carvão é responsável pela geração de diferentes sub-produtos. Entre esses, está a pirita que acidifica a água e acelera o processo de solubilização de metais. Como conseqüência, o ambiente torna-se ácido e rico em metais pesados, os quais selecionam os microrganismos capazes de sobreviver nestas condições. Esses microrganismos podem, por sua vez, serem empregados como agentes para a biorremediação de áreas contaminadas com metais pesados. No presente trabalho é descrito o isolamento e a caracterização de bactérias, fungos e leveduras resistentes aos metais zinco, níquel e cádmio.