In our article, the most ancient organisms - bacteria, will be examined. The way of feeding and the habitat of these organisms are very diverse. How are these characteristics interconnected?
General characteristics of bacteria
Bacteria are a group of unicellular microscopic organisms. They are prokaryotes. This means that their cells do not contain a formed nucleus. Their genetic material is represented by a circular DNA molecule located directly in the cytoplasm.
The forms of bacterial cells are very diverse. They can take the form of a ball, sticks, bunch of grapes, spirals, stars, cube, etc. The surface apparatus of bacteria is represented by a permeable membrane, mucous capsule, and cell wall consisting of murein or pectin. In the cytoplasm of prokaryotes are ribosomes and cytoskeletal elements.
Bacteria: diet and habitat
Due to the simplicity of the structure, bacteria have mastered all habitats. They are found in water, soil, air, rocks, hot springs, on the surface of the body, in the internal organs of plants, animals and humans. By the method of nutrition, bacteria are both auto- and heterotrophs.
The former contain chloroplasts in their cells, due to which photosynthesis is carried out. As a result, glucose carbohydrate is formed, which is used to carry out various vital processes. Organisms that use solar energy for the synthesis of organic substances are also called phototrophs. These include green, purple, and cyanobacteria.
Another group of autotrophic bacteria uses the energy of chemical bonds for life. They transform complex compounds into simpler ones. This process is called chemosynthesis. Examples of such organisms are sulfur, iron and nitrogen-fixing bacteria.
The group of heterotrophic prokaryotes is also quite numerous. The source of their nutrition depends on the habitat. Depending on this, three groups of bacteria are distinguished:
- saprotrophs;
- parasites;
- symbiotic organisms.
Let's consider each of them in more detail.
Saprotrophs
This group of bacteria lives in all environments that contain organic substances. It can be soil, plant and animal organisms. For example, rotting bacteria are saprotrophs by the method of nutrition. They decompose organics, extracting nutrients from it.
Such is the way of feeding lactic acid bacteria. Their ability to ferment carbohydrates is widely used in the food industry. Kefir, fermented baked milk, cottage cheese, yogurt - all these are vital products of prokaryotes of this species.
Parasites
Parasitic bacteria, the method of nutrition of which is also heterotrophic, live inside or on the surface of other organisms. Eating the host's vital products, they cause serious illness. For example, a dysenteric bacillus, which multiplies in the intestines, causes weakness, fever, headache, upset stool - all these are manifestations of dysentery. Salmonella disease, typhoid fever and cholera are often referred to as “dirty hands disease”. All of them are caused by the ingestion of parasitic prokaryotes.
Dangerous diseases of humans and animals are tuberculosis, anthrax, tetanus, tonsillitis, diphtheria, glanders, and brucellosis. The mechanisms of their ingestion are different:
- drinking contaminated water or foods;
- airborne droplet;
- non-compliance with hygiene.
Symbiotic bacteria
Many organisms are able to enter into mutually beneficial relationships with representatives of other kingdoms of wildlife. Bacteria are no exception. The method of nutrition of representatives of this group is also heterotrophic. However, they feed on the finished substances of other organisms without harming them. In addition, such cohabitation has many benefits.
An example of such a manifestation is nitrifying bacteria that live in the roots of legumes. Getting there from the soil through cracks in the integumentary tissue, they begin to multiply actively. As a result, small but numerous bubbles form. This type of microorganism is able to fix nitrogen, which is part of the air, and convert it into a form accessible to plants. At the same time, they receive nutrients from plants that are in aqueous solution.
Symbiotic human bacteria are prokaryotes that live in his intestines. Here they produce enzymes that further contribute to the breakdown of a number of organic compounds. Bacteria of the skin and mucous membranes prevent the resettlement of "foreign" prokaryotes.
So, bacteria are unicellular prokaryotic organisms. They can both independently synthesize organic substances (autotrophs) and eat ready-made (heterotrophs).