Bacteria are microscopic, single-celled organisms forms colonies that present anywhere in diverse environments. These organisms can live in soil, the ocean and inside the human gut.
Humans’ relationship with bacteria is complex. Sometimes bacteria lend us a helping hand, such as by curdling milk into yogurt or helping with our digestion. In other cases, bacteria are destructive, causing diseases like pneumonia and methicillin-resistant Staphylococcus aureus (MRSA).
How many shapes of bacteria?
Bacteria are classified into five groups according to their basic shapes: spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochaetes). They can exist as single cells, in pairs, chains or clusters.
What is the structure of bacteria?
Bacterial cell structure is different from plant and animal cells. Bacteria are prokaryotes, which means they have no nucleus.
A bacterial cell consist of :
Capsule: An outer layer around the cell wall in some bacteria.
Cell wall: A layer that is made of a polymer called peptidoglycan. The cell wall gives the bacteria its shape. It is located outside the plasma membrane . The cell wall is thicker in some bacteria, called Gram positive bacteria.
Plasma membrane: Found within the cell wall, this generates energy and transports chemicals. The membrane is permeable, which means that substances can pass through it.
Cytoplasm: A gelatinous substance inside the plasma membrane that contains genetic material and ribosomes.
DNA: This contains all the genetic instructions used in the development and function of the bacterium. It is located inside the cytoplasm.
Ribosomes: The place where proteins are made, or synthesized. Ribosomes are complex particles made up of RNA-rich granules.
Flagellum: This is used for movement.Some bacteria have more than one.
Pili: These hair-like appendages on the outside of the cell allow it to stick to surfaces and transfer genetic material to other cells. This can contribute to the spread of diseases in humans.
What is the mod of nutrition of bacteria?
Bacteria feed in different ways.
Heterotrophic bacteria : Get their energy through consuming organic carbon. Most absorb dead organic material, such as decomposing flesh. Some of these parasitic bacteria kill their host, while others help them.
Autotrophic bacteria : Make their own food through:
Photosynthesis: Using sunlight, water and carbon dioxide.
Chemosynthesis: Using carbon dioxide, water, and chemicals such as ammonia, nitrogen, sulfur, and others
Bacteria that use photosynthesis are called photoautotrophs. Some types, for example cyanobacteria, produce oxygen. These probably played a vital role in creating the oxygen in the earth’s atmosphere. Others, such as heliobacteria, do not produce oxygen.
Those that use chemosynthesis are known as chemoautotrophs.
How bacteria reproduce?
Bacteria may reproduce using the following methods:
These microscopic organisms reproduce by both the Sexual and Asexual methods. Sexual reproduction in bacteria occurs in the form of genetic recombination and the asexual reproduction occurs by the formation of endospores.
Most bacteria reproduce by the process known as binary fission . Conceptually this is a simple process; a cell just needs to grow to twice its starting size and then split in two. But, to remain viable and competitive, a bacterium must divide at the right time, in the right place, and must provide each offspring with a complete copy of its essential genetic material. Bacterial cell division is studied in many research laboratories throughout the world. These investigations are uncovering the genetic mechanisms that regulate and drive bacterial cell division. Understanding the mechanics of this process is of great interest because it may allow for the design of new chemicals or novel antibiotics that specifically target and interfere with cell division in bacteria
Sexual Reproduction in Bacteria is usually carried out in three ways:
Transformation : In this process, the DNA from the capsulated bacteria is transferred into a non-capsulated bacteria.
Transduction : In this process, the DNA is transferred from one bacterial cell into another bacterial cell with the help of a bacteriophage. This process is known to occur in several bacterial species such as Escherichia, Micrococcus, Salmonella, etc.
Conjugation : It is a process in which the genetic material of a bacterial cell of a particular strain is transferred from a donor or male into that of another bacterial cell recipient or female of a different strain. The donor cells are known to possess a sex factor or F factor and the recipient cell does not have this factor and hence it is described as F- strain.
How bacteria are helpfull and harmful?
Bacteria and Humans
Bacteria and humans have many important relationships. Bacteria make our lives easier in a number of ways. In fact, we could not survive without them. On the other hand, bacteria can also make us sick.
Benefits of Bacteria
Bacteria provide vital ecosystem services. They are important decomposers. They are also needed for the carbon and nitrogen cycles. There are billions of bacteria inside the human intestines. They help digest food, make vitamins, and play other important roles. Humans also use bacteria in many other ways, including:
- Creating products, such as ethanol and enzymes.
- Making drugs, such as antibiotics and vaccines.
- Making biogas, such as methane.
- Cleaning up oil spills and toxic wastes.
- Killing plant pests.
- Transferring normal genes to human cells in gene therapy.
- Fermenting foods .
Bacteria and Disease
You have ten times as many bacteria as human cells in your body. Most of these bacteria are harmless. However, bacteria can also cause disease. Examples of bacterial diseases include tetanus, syphilis, and food poisoning. Bacteria may spread directly from one person to another. For example, they can spread through touching, coughing, or sneezing. They may also spread via food, water, or objects.
How bacterial diseases are spread?
Bacteria and other pathogens can spread is by vectors. A vector is an organism that spreads pathogens from host to host. Insects are the most common vectors of human diseases. Figure below shows example.
Humans have literally walked into some new bacterial diseases. When people come into contact with wild populations, they may become part of natural cycles of disease transmission. Consider Lyme disease. It’s caused by bacteria that normally infect small, wild mammals, such as mice. A tick bites a mouse and picks up the bacteria. The tick may then bite a human who invades the natural habitat. Through the bite, the bacteria are transmitted to the human host.