Interspecies interactions are well known among soil-dwelling bacteria belonging to the genera Bacillus and Pseudomonas. When co-cultured, Pseudomonas chlororaphis competes for space with Bacillus subtilis, infiltrates their colonies and kill them. Killing of vegetative cells of $B$. subtilis by $P$. chlororaphis requires physical contact and the type-VI secretion system (T6SS) to inject the toxins. B. subtilis undergo sporulation and use it as an escape/defense mechanism to avoid killing by $P$. chlororaphis. On the other hand, when $P$. chlororaphis are co-cultured with $B$. amyloliquefaciens, colonies have distinct zones with no physical contact. In this scenario, $P$. chlororaphis utilizes a different secretion system, T2SS, to secrete secondary metabolites that inhibit the growth of B. amyloliquefaciens. Bacillaene, a bacteriostatic compound, is produced by B. amyloliquefaciens that antagonizes P. chlororaphis. The interaction between $P$. chlororaphis with $B$. subtilis and $P$. chlororaphis with B. amyloliquefaciens, respectively, represents:

• Correct answer
  A

  predation and competition.
• B

  commensalism and competition.
• C

  competition and predation.
• D

  commensalism and mutualism.

Hence, the correct answer is option: 'A'.