Question

The cultures of Alexander Fleming consisted of
A. Streptococcus
B. Staphylococcus
C. Bacillus
D. Clostridium

Answer 1

Hint: Sir Alexander Fleming, a Scottish microbiologist and physician is well renowned for his discoveries of antibiotic penicillin and extraction of enzyme lysosome. He was a researcher at St Mary’s Medical School at London University.

Complete answer:
While working as an immunobiologist researcher at St Mary’s Medical School, Alexander Fleming discovered an isolated enzyme lysosome and demonstrated its bacterial growth inhibiting properties. The most renowned discovery of Alexander Fleming is the discovery of penicillin, which had antibacterial properties that was found to be effective against all gram positive bacteria causing pneumonia, scarlet fever, gonorrhoea etc. Fleming has been investigating the properties of staphylococcus bacteria. During his investigation, he accidently left the inoculated bacteria in a Petri dish instead of placing it in an incubation chamber. The petri dish was placed near the window. Upon his return to his lab after a gap of two weeks, he found that the culture was contaminated with a fungus and the colonies of staphylococcus bacteria near the fungus was found to be destroyed. The other colonies that were far away from the fungus were growing normally. After further investigation, he identified the mold as a member of the genus Penicillium. He grew the mold in a pure culture and found that the culture broth contained antibacterial substances.

> Option A, Streptococcus is a group of gram positive bacteria with spherical shapes. They have a tendency to form pairs or chains which may appear bent or twisted. These bacteria are the causative agent of many throat infections, pneumonia, and bloodstream infections.

> Option C, Bacillus is a type of gram positive bacteria with an elongated rod-shaped structure. They can be obligate aerobes and facultative anaerobes and are universal in appearance. They are the causative agents for various diseases such as food poisoning, and anthrax. They are an important organism that is responsible for food spoilage. Some species of bacillus can produce toxins that bear antimicrobial properties and can kill pests and harmful fungi.

> Option D, Clostridium belongs to a genus of rod-shaped bacteria which are usually gram positive. They are found in soil, water, and in the intestinal tracts of human and other animals. The group of bacteria belonging to this genus causes several pathogenic conditions in humans. They are the causative agent of botulism and tetanus.

Hence, The correct answer is option (B).

Note: During his experiments on the bacteria staphylococcus, he accidently made the discovery of the first antibiotic. An open uncovered Petri dish became contaminated with fungal spores which inhibited the growth of the bacteria. Further isolation and identification of the mold revealed it to be a member of the genus Penicillium. He was of the opinion that it was not the mold but some kind of mold juice that destroyed the bacteria and named it as penicillin.