Low intensity microwave radiation on E . coli host system for its compatibility and transformation efficiency

Resonance-like biological effects of microwave radiation at frequencies of approximately 50 KHz on the growth rate of E. coli and on DNA have been reported in several scientific publications. In order to explore these non-thermal effects, we have measured the growth rate and the absorption spectrum of E. coli, irradiated by microwaves in the frequency range from 10 to 50 KHz. In addition, the effect of this radiation on plasmid DNA was studied by measuring plasmid transformation efficiency. Both the growth rate variations with varying frequency and the variations in the result of the plasmid transformation efficiency experiments were found to be statistically insignificant. The experimental results indicate that resonance effects are likely to have high transformation efficiency in this particular frequency range.

typhimurium when the growth rate varied by nutrition.Despite these and other important discoveries supporting the view that the rate of bacterial growth can be understood, that goal has not yet been attained.This study was carried out to investigate plasmid amplification, transformation efficiency and other cell diffe-rentiation by microwave irradiation in E.coli.

Amplification by Microwave Exposure
In these experi-ments, we used 10 KHz to 50 KHz microwaves in 55 W. (Imperial V-8505T).The experiments carried out at 37°C (+ 1 °C).Bacteria in logarithmic growth phase were exposed to microwave for 5 min every 15-min for 150 min.This irradiation procedure provided maximum irradiation effects.

Nucleic acid and protein determination
Protein content was determined by Lowry's method with BSA as standard 6 .Nucleic acid content was determined by optical density analytical measurement in UV spectrophotometer 7 .

Plasmid puri-fication
Plasmid content in E.coli of 5-10 colonies was randomly selected and plasmid was prepared from 20ml culture.Plasmids from the bacteria were isolated by alkaline extraction method 8 , where the lysozyme concentration was increased from 1 to 3 mg/ml and lysozyme was added to 100 units/ml.Plasmid DNA was purified by hydroxyapatite chromatography 9 .

Amplification by Chloramphenicol
Bacteria were amplified with 170µg/ml of chloramphenicol that concluded by analogy to obtain the results of microwave irradiation.

1.
It was identified that chloramphenicol inhibited the growth at a nearly 20%, Microwave inhibited the growth at a nearly 4% (Table 1, 2).

2.
It was determined that microwave application decrease the protein amount at a rate of 6%, while chloramphenicol appli-cation did at a It was also found that the plasmid amount increased by 38% with chloramphenicol application; however, this increase was at a rate of 21% with microwave irradiation.4.
It was further found that the transformation efficiency with microwave treatment was observed maximum when exposed at 20 KHz for 5 minutes (Table 3).

DISCUSSION
As a result of the experiments carried out, the growth has been affected ad-versely from both microwave irradiation 10 and chloramphenicol application helps us think that they are effective, even diffe-rently, on division factors.The DNA amount decreases at the same rate as growth, although equal amounts of bacteria are taken in microwave irradiation; bring to mind that DNA is not replicated in cells 11,1 .On the other hand in the chloramphenicol applica-tion, the decreasing of DNA amount with respect to the growth leads us to think that replication occurs, but that division does not.That protein amount is higher after microwave irradiation with respect to chloramphenicol indicates that microwave is so effective as chloramphenicol on protein synthesis mechanisms.To bring to mind that, since mi-crowave irradiation inhibits peptidyl transferase enzyme stability, chloramphenicol degrades portionally tertiary structure of one are more enzymes regarding the activity of protein synthesis system or that enzyme-substrate relation may have been degraded from ion unbal-ance or enzyme-substrate interaction 12 .Thus, it appears that the amplification formed by microwave irradiation does not constitute alternative when the time is not considered.However, when short time ir-radiation like 5 minutes is needed, it is an application that can constitute as an alter-native for amplification by antibiotics.