This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
True about corynebacterium diptheria are all except : 
Select and explain. 
A. Iron is required for toxin production, B. Toxin production is responsible for local reaction, C. Nonsporing, noncapsular and non motile, D. Toxin production is by lysogenic conversion
B: Toxin production is responsible for local reaction
Answer: B: Toxin production is responsible for local reaction 
Explanation: “Mechanical complications of diptheria are due to the membrane while the systemic effects are due to the toxin.”

Toxin acts mainly systemically though there are partial local effects.
It has affinity for myocardium, adrenals and nerve endings.
Toxin acts by inactivating EF-2 thus inhibiting protein synthesis.
Toxin production is influenced by iron concentration in the medium. Toxin production is optimal at 0.14 μ g/ ml and is suppressed at 0.5 μ g/ml.
Toxigencity of diptheria bacullus depends on symbiotic bacteriophages so it shows lysogenic or phage

conversion i.e. nontoxigenic strain →→→→→ toxigenic strain by infecting with beta phage.
Remember :

Corynebacteria are gram positive, non acid fast, non sporing, non capsulated, non motile bacteria.
It contains polar bodies or volutin or babes-ernst or metachromatic granules of polymetaphosphate which are more gram positive.
Granules are also stained by loeffler’s methylene blue, Albert’s, Neisser’s and ponder’s stain.