Locomotion of Bacteria
6.4.5 Locomotion in Bacteria
Most bacteria possess flagella as locomotory appendages, which help in gliding, twitching motility, or change of buoyancy. The spirochetes have helical bodies which help them to twist about as they move. During twitching motility pili help in anchoring.
Flagella are commonly found in bacilli and spirilla while most cocci are without flagella known as atrichous. There are two types of arrangement of flagella, i.e., polar and peritrichous. Polar flagella are situated at one end or both ends of bacteria and divided i
types.
Monotrichous:
single flagellum at one end, e.g., vibrio. Lophotrichous: a cluster of flagella at one, end e.g., spirillum..
Amphitrichous:
Amphilophotrichous tuft of flagella at both ends. Peritrichous: flagella are arranged all around the Salmonella typhi.
6.4.6 Structure of Flagella
A flagellum is made of three parts, i.e., a basal body, a short curved hook, and a helical filament, and consists of several protein chains. The protein of flagella is flagellin.
6.4.7 Genomic Organization of Bacteria
The genome of most bacteria consists of a single circular chromosome, containing 1,60,000 to 1,22,00,000 base pairs. It is located in a specific region of cytoplasm called nucleoid or nuclear region (no membrane-bounded nucleus).
In addition to its single chromosome, the bacteria also possess extrachromosomal DNA rings of small size known as plasmids. The plasmids are self-replicating and contain genes for drug resistance, heavy metals, and insect-resistant genes.
6.5 Nutrition in Bacteria
Bacteria like other organisms, need nutrients for their growth, reproduction, and other vital activities. They are divided into two groups: autotrophic and heterotrophic bacteria.
6.5.1 Autotrophic bacteria
These bacteria synthesize their own food from simple inorganic substances. They obtain all the carbon from inorganic carbon compounds such as carbon dioxide. The autotrophic bacteria are further divided into two groups namely photoautotrophic and chemoautotrophic.
Photoautotrophic or Photosynthetic Bacteria:
These bacteria possess chlorophyll, located either in the membrane of their mesosomes or freely dispersed in the cytoplasm. Bacteria have a unique type of chlorophyll that is chlorophyll and fairly known as bacteriochlorophylls. Photoautotrophic bacteria use the energy of sunlight H, S as an "H" source (instead of H, O) and liberate "S" instead of O, to make carbohydrates (organic food) from CO,.
Heterotrophic Bacteria:
bacteria cannot prepare their own food. They depend on organic compounds prepared by other organisms. Two types of heterotrophic bacteria are saprotrophic and parasitic bacteria.
Many bacteria are heterotrophic, the A Saprotrophic Bacteria or Saprobs (Gk. Sapro = rotten)
Como know?
These bacteria get their food from dead and decaying organic matter (Humus). They have a powerful enzyme system that helps in the breakdown of complex organic compounds into simple substances and uses the energy released in the process. Examples: Pseudomonas, Azobacter.
(Note: The chemicals released during the breakdown of organic substances become available to other organisms, therefore, saprobes are called recyclers of nature. They clean the earth by their action, thus also called the scavengers of the earth).
Parasitic Bacteria:
These bacteria get their food from the host and depend on host enzymes to make food. Parasitic bacteria include pathogenic bacteria (disease-causing) examples are Mycobacterium, and Streptococcus pneumoniae.
Respiration in Bacteria:
Respiration in bacteria may be aerobic and anaerobic. Aerobic bacteria need oxygen to break down food, e.g., Pseudomonas. Anaerobic bacteria break down food without oxygen, e.g., Spirochetes.
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