"Trade-off" in Antarctic bacteria: limnetic psychrotrophs concede multiple enzyme expressions for multiple metal resistance.

The present study examines the metal and antibiotic resistant bacteria in ice and water from lakes east and west of the Indian base camp (Maitri) in Antarctica. The isolates from western and eastern lakes showed distinct geographical differences in properties like metal resistance and enzyme expression. This may be attributed to high organic loading in the lakes on the west of Maitri. However, there was no marked geopraphical distinction in antibiotic resistance between the lakes. Bacteria from the lakes on the eastern side showed resistance to three or more metals including mercury while, those from the western were resistant to only 1-2 metals excluding mercury. Multiple enzyme expression was more pronounced in the lakes on the western side. On the eastern side multiple metal resistance was encountered in bacterial isolates associated with fewer enzyme expressions suggesting a "trade-off". Thus these Antarctic isolates from the east trade their ability to express multiple enzymes for developing resistance to multiple metals including mercury.

Metal and antibiotic-resistance in psychrotrophic bacteria from Antarctic Marine waters.

In the wake of the findings that Antarctic krills concentrate heavy metals at ppm level, (Yamamoto et al. 1987), the Antarctic waters from the Indian side were examined for the incidence of metal and antibiotic-resistant bacteria during the austral summer (13th Indian Antarctic expedition) along the cruise track extending from 50 degrees S and 18 degrees E to 65 degrees S and 30 degrees E. The bacterial isolates from these waters showed varying degrees of resistance to antibiotics (Chloramphenicol, ampicillin, streptomycin, tetracycline and kanamycin) and metals (K(2)CrO(4), CdCl(2), ZnCl(2) and HgCl(2)) tested. Of the isolates screened, about 29% and 16% were resistant to 100 ppm of cadmium and chromium salt respectively. Tolerance to lower concentration (10 ppm) of mercury (Hg) was observed in 68% of the isolates. Depending on the antibiotics the isolates showed different percentage of resistance. Multiple drug and metal-resistance were observed. High incidence of resistance to both antibiotics and metals were common among the pigmented bacterial isolates. Increased resistance decreased the ability of bacteria to express enzymes. The results reiterate previous findings by other researchers that the waters of southern ocean may not be exempt from the spread of metal and antibiotic-resistance.