
Concept explainers
Describe why a microbial mat has green, reddish-pink, and black layers.

To review:
The microbial mat having green, reddish-pink, and black layers.
Introduction:
Biofilm is a thin layer or sheet, which is composed of living organisms such as microbes that are attached to the surfaces of solids or in between the air and water faces. A microbial mat is a dense, multilayered, thick, and highly organized form of a biofilm, which is composed of colonies of mainly archaea and bacteria. These mats provide an important model for the study of microbial interactions and microbial communities.
Explanation of Solution
The microbial mats consist of several layers that are visually distinguishable. There are mainly three colored layers, which represents the growth of different microbial communities. The green colored layer is the topmost layer that consists of mainly cyanobacterial community and appears green due to the presence of green photosynthetic pigments in them and makes the organic materials. Below this, is the pink-colored layer that represents the community of purple sulfur bacteria. These are anaerobic phototrophs. The lowermost layer is black in color, which represents the community of sulfate-reducers. These are obligate anaerobic bacteria that metabolize the organic components synthesized by the upper layers of the microbial mat.
Therefore, the microbial mat represents the distinct layers of the microbial communities that are present altogether. The uppermost layer is green due to the cyanobacterial community, the pink-colored one is present in middle comprising of purple sulfur bacteria and the lowermost is black in color showing the sulfate-reducing bacteria.
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Chapter 28 Solutions
Nester's Microbiology: A Human Perspective
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