QVprep Biology Lessons

Bacteria, Classification of Bacteria, Where Bacteria are found?, How do bacteria reproduce?, How do bacteria survive?

Topics

Subtopic

Bacteria: Bacteria are single celled microbes. The cell structure is simpler than that of other organisms as there is no nucleus or membrane bound organelles. The DNA is found as a single loop. Some bacteria have circular, extra-chromosomal DNA called plasmid. The plasmid contains genes that give the bacteria some selective advantage like antibiotic resistance.


Classification of Bacteria: Bacteria are classified into 5 groups according to their basic shapes: spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochetes). They can exist as single cells, in pairs, chains or clusters.


Where Bacteria are found?: Bacteria are found in every habitat on Earth. There are approximately 10 times as many bacterial cells as human cells in the human body. A lot of these bacterial cells are found lining the digestive system. Some bacteria live in the soil, others cause food spoilage, a few bacteria produce useful products and few bacteria are parasites that cause disease.


How do bacteria reproduce?: Bacteria reproduce by binary fission through which is a single cell, divides into two identical daughter cells. The DNA of the bacterium divides into two and then the cell elongates and splits into two daughter cells each with identical DNA to the parent cell.


How do bacteria survive?: Some bacteria can form endospores. These are dormant structures, which are extremely resistant to hostile physical and chemical conditions such as heat, UV radiation and disinfectants. This makes destroying them very difficult. Many endospore-producing bacteria are pathogens, for example Bacillus anthracis is the cause of anthrax.