Question

Chromatium is a type of
A. Chemotroph
B. Herbivore
C. Phototroph
D. None of the above

Answer 1

Hint: The Chromatium is a primitive bacteria which are known for their ability of carbon fixation and they have a marine habitat. They fix carbon in the deeper levels without the release of oxygen. They utilize photons as energy sources to carry out the process.

Complete answer:
As given in the hint, that the Chromatium bacteria live in the aquatic habitat and in the aquatic habitats’ herbivore organisms are not found because they rely on the grass for meeting their nutritional requirement and grasses do not grow in the water. So, we can rule out option B easily.
The other option is chemotroph and phototroph, normally both the process involves chemical reaction but in phototroph the light energy plays the driving force of the reaction. So, if we look at the mechanism of production of food in the bacteria then we will get the right answer.
The bacteria Chromatium contains bacteriochlorophyll. The chlorophyll in plants help them in capturing the sunlight. Same in the case of bacteria happens, the bacteriochlorophyll helps it in capturing light energy in the form of photons and the fixation of carbon occurs inside the bacteria. But the catch here is that, in this carbon fixation the oxygen gas is not evolved. The requirement of carbon for the production of food by the bacteria is taken care of by the presence of sulfur in the water. The sulfur is present in the inorganic form.

Therefore, the correct answer is the Option C.

Note:
All the phototrophs are somewhat similar to the chemotrophs because they also rely on the chemical process which takes place which help them in preparing their food. The utilization of energy sources is what is different in both organisms.