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Superkingdom Prokaryotae

Reproduction and nutrition

chemoheterotrophs, photoheterotrophs, Nitrosomonas, inorganic molecules, asexual reproduction

Reproduction

Most prokaryotes multiply by the asexual process of binary fission, in which the DNA of the organism replicates in the cytoplasm, the cell divides in two, and one DNA molecule passes to each newly formed cell. In addition, some prokaryotes undergo various processes of genetic recombination. For example, in the process called transformation, a bacterium removes one or more genes from one organism and incorporates the genes into its own genetic makeup. In conjugation two organisms exchange genes. In transduction a virus transports bacterial genes from one organism to another. Gene transfers account for the appearance of new biochemical traits in prokaryotes.

Conjugation, in biology, the most simple form of sexual reproduction, as contrasted with asexual reproduction. It is observed in one-celled organisms when two similar organisms join together and exchange genetic material contained in their nuclei. After the exchange, the organisms separate. Commonly they each reproduce afterward by fission (splitting apart). Some organisms fail to do so, however, apparently benefiting simply from the exchange.

Nutrition

Like most organisms, prokaryotes require carbon and energy to create nutrients such as carbohydrates, proteins, lipids, and nucleic acids. Prokaryotes obtain carbon and energy from a variety of sources. Certain prokaryotes use carbon dioxide as their carbon source. Called autotrophs, these prokaryotes derive energy from different sources, such as photosynthesis or inorganic molecules. Photoautotrophs, including the cyanobacteria and the green sulfur and purple sulfur archaebacteria, derive their energy from light. Chemoautotrophs, such as the soil bacteria Nitrobacter and Nitrosomonas, derive their energy from inorganic compounds such as hydrogen sulfide, ammonia, and iron.

Heterotrophs are organisms that rely on ready-made organic compounds such as glucose or alcohol for their carbon source. Heterotrophs obtain energy by degrading organic molecules, such as plant or animal matter. A small group of bacteria, the photoheterotrophs, use light as their energy source, while chemoheterotrophs use organic compounds for both their carbon and energy sources.



Article key phrases:

chemoheterotrophs, photoheterotrophs, Nitrosomonas, inorganic molecules, asexual reproduction, cyanobacteria, hydrogen sulfide, prokaryotes, cytoplasm, inorganic compounds, transduction, genetic makeup, carbon source, fission, nucleic acids, photosynthesis, lipids, animal matter, bacterium, organic compounds, ammonia, energy sources, nuclei, conjugation, carbon dioxide, carbohydrates, proteins, glucose, organisms, Nutrition, nutrients, alcohol, iron, biology, cell, energy, transformation, plant, example, Reproduction, addition

 
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