among the following which microorganism is photoautrophic in nature

1. ferrobacillus
2. beggiotoa
3. nitrosomonas and nitrosococcus
4. green sulphur bacteria and purple bacteria

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​Correct Answer is 4. Green sulphur bacteria and purple bacteria
Green sulphur bacteria and purple bacteria are photoautotropic in nature. They are photosynthetic in nature but are anaerobic and no O₂is evolve during photosynthesis.
Beggiatoa is sulphur oxidising bacteria.
Ferrobaccilus obtains energy by oxidising ferrous compounds to ferric forms.
Nitrosomonas and Nitrosococcus obtains energy by oxidising ammonia into nitrite.
Nitrosomonas, Nitrosococcus, Beggiotoa andFerrobaccilus are all chemoautotropic bacteria.