<prompt> Chinese letter arrangement is seen in: March 2009 2011M.tuberculosisCorynebnacterium diphtheriaChlamydia trachomatisM. leprae  <response>: Ans. B: Corynebnacterium diphtheria Nonpathogens that resemble Corynebacterium diptheriae in appearance are termed diptheroids. The arrangement of the bacteria provide a clue to distinguish the pathogen Corynebacterium diptheriae from the nonpathogenic diptheroids. C. diptheriae bacteria form 90 degree angles to one another, forming Xs, Ys, or Chinese letters. In contrast, diptheroids are often in parallel arrangements called palisades. The diagnostic significance of metachromatic granules arises from the fact that the causative agent of diptheria, Corynebacterium diptheriae, characteristically produces metachromatic granules. 