The growth rate of the phototrophic purple bacterium Rhodobacter is about twice as fast when the organism is grown phototrophically in a medium containing malate as the carbon source as when it is grown with CO2 as the carbon source (with H2 as the electron donor). Discuss the reasons why this is true, and list the nutritional class in which we would place Rhodobacter when growing under each of the two different conditions.
To explain:
The growth rate of phototrophic purple bacterium Rhodobacter is about twice as fast when the organism is grown phototrophically in a medium which contain malate as the carbon source or as it is grown with CO2 as the carbon source (with H2 as the electron donor). Discuss the reason why this is true, and list the nutritional class in which we would place the bacterium Rhodobacter when growing under both the two different conditions.
Introduction:
The purple photosynthetic bacteria are Proteobacteria that have the ability of producing their own food through the process of photosynthesis. They are pigmented with bacteriochlorophyll a or b together with the various carotenoids. It gives them colors that range between orange, red brown, and purple. It may be divided into two groups include purple non-sulfur bacteria (Rhodospirillaceae) and purple sulfur bacteria chromatiales.
Explanation of Solution
In taxonomy, the Rhodobacter belongs to the genus of Rhodobacteraceae. It is used as a model organism to study the bacterial photosynthesis that include Rhodobacter capsulatus and Rhodobacter sphaeroides. Rhodobacter is a purple bacterium, which can obtain the energy through the photosynthesis. An organism, which is able to carry out the process of photosynthesis, is called as the phototrophs. It can be further divided into photoheterotrophs and photoautotrophs.
An organism that carry out the photosynthesis by using sunlight as the source of energy is called as photoautotrophs and it can grow by using carbon dioxide as the only source of carbon and using sunlight as its energy source. The water and carbon dioxide are converted into organic materials. This process is used in the cellular functions such as respiration and biosynthesis.
The photoheterotrophic organisms’ uses sunlight as the energy but it cannot use carbon dioxide as the source of organic compound. Instead, it uses carbon as the organic source. Thus, Rhodobacter is grouped as the photoautotroph when it uses the carbon dioxide as its carbon source. The organism Rhodobacter grown in a medium containing malate as the carbon source use then, it can be placed in the nutritional class of photoheterotrophs. Therefore, the bacterium Rhodobacter is growing twice as fast and well as the photoheterotrophs than as photoautotrophs.
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Chapter 14 Solutions
Brock Biology of Microorganisms (15th Edition)
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