Dr.K.Sivasubramani

When we tried to assess the quality of air with settle plate technique we isolated some spider web like colonies. They might be  Bacillus mycoides . It is quite amazing that this bacteria has two types of curvature ie., clockwise and counter clockwise. A strain can produce either curvature not both. The direction of curvature can be changed by altering NaCl concentration. Source and Further reading http://crf.flib.u-fukui.ac.jp/dspace/bitstream/10461/14980/1/kiyou46.p9-14.pdf

In a discussion, we were talking about the history of Gram staining. Slowly talk shifted about the use of crystal violet MacConkey agar to inhibit  Gram positive bacteria. But how a simple dye inhibit a group of bacteria and become a selective agent? Here comes the answer, "The mode of action put forward by Steam & Stearn (1928) that the action of crystal violet is due to the formation of an unionized complex of bacteria with dye, is supported. Gram-negative organisms, such as  E. coli , have high isoelectric points and contain less acidic components than Gram-positive bacteria which usually have lower isoelectric points, so the former combine with crystal violet less readily and are more resistant to the dye. " Very happy to discuss science with youngsters... Source: http://onlinelibrary.wiley.com/doi/10.1111/j.2042-7158.1967.tb09550.x/abstract Image Courtesy: http://www.evidentcrimescene.com