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The doubling time of E. coli is 20 minutes in media containing methionine. If the media lacks methionine the doubling time is 30 minutes. Draw and label comparative growth curves. E. coli was used as the negative control for Gram Staining in Lab. Describe it. Use a diagram or diagrams and label it.

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Q.3.

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E.coli is used as negative control in gram staining in bacteria, as initiation of DNA replication in E. coli requires synthesis of a protein whose production is correlated with total protein synthesis. Once replication is initiated, however, reinitiation will occur if all further protein synthesis is prevented; a small amount of protein synthesis is sufficient to prevent this unregulated reinitiation. This shows that the initiation of DNA replication is under negative control. A mechanism for the control of DNA replication is proposed; in this mechanism a replication repressor is synthesized periodically, while an antirepressor protein is synthesized continuously.

Escherichia coli is a Gram-negative, rod-shaped bacterium that is easily found in the lower intestine of warm-blooded organisms. Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans. The harmless strains are part of the normal flora of the gut, and their hosts can be benefited by the producing vitamin K2 by E.coli , and also prevents the establishment of pathogenic bacteria in the gut. E. coli and related bacteria constitute about 0.1% of gut flora, and fecal-oral transmission is the major route through which pathogenic strains of the bacterium cause disease. In gram-ve strain, they appear as pink or red in colour.

FLAGELLA OUTER MEMBRANE -PILI Eschemichia col