Conidia Formation: The formation of conidia takes place in filamentous bacteria such as Streptomyces through the formation of a transverse septum at the apex of the filament. The part bearing the conidia is called the conidiophore and after it is detached from the mother cell, in a suitable substratum it germinates giving rise to new mycelium.
This type of asexual reproduction is also called fragmentation. Budding: In this method of reproduction, the bacterial cell develops a small swelling at one side which continuously increases in size. At the same time, the nucleus also undergoes division where one part with some cytoplasm enters the swelling and the other part remains with the mother cell. The outgrowth is called the bud and it eventually gets separated from the mother cell by a partition wall. This method of reproduction also comes under vegetative reproduction in bacteria.
Example: Rhodomicrobium vannielii. Cysts: Cysts are formed by the deposition of additional layers around the mother cell and are the resting structure during unfavourable conditions. When conditions are favourable again, the mother cell behaves like its normal self again. Example: Azotobacter. Reproduction through endospore formation: Endospores in a bacterial cell are formed during stressful conditions such as desiccation and starvation.
They contain a central protoplast, and a core consisting of DNA, ribosomes, enzymes and the t-RNA, everything necessary for the formation of a new cell. Each daughter cell is a clone of the parent cell.
When conditions are favourable such as the right temperature and nutrients are available, some bacteria like Escherichia coli can divide every 20 minutes. This means that in just seven hours one bacterium can generate 2,, bacteria. After one more hour the number of bacteria will have risen to a colossal 16,, 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 nasty pathogens, for example Bacillus anthracis , the cause of anthrax. Educational resource for students: Observing bacteria cultures in a Petri dish and learning about colony morphology.
The organisms that cause tuberculosis in humans and animals, Mycobacterium tuberculosis and Mycobacterium bovis , are featured in this edition of Microbiology Today alongside Mycobacterium leprae , the cause of leprosy, and Mycobacterium ulcerans , which causes Buruli ulcer. Often, the first things that come to mind when we think about microbes in the built environment are damage, decay, discolouration and staining to building materials and their surfaces.
Tuberculosis TB is a debilitating multi-organ disease caused by the bacterium Mycobacterium tuberculosis. The most important form of the disease is pulmonary TB, an infection of the lungs and respiratory tract. They are an extremely diverse and abundant group of organisms and are important for a range of reasons.
Bacteria are important for a number of reasons. They perform functions that make them important to other life forms plus they are important economically in a number of industries. Some species of bacteria cause disease and infections, but far more commonly, bacteria are beneficial.
They are so important in our own bodies that if all of the bacteria from inside our bodies were removed, we would die without their help. Bacteria that live inside the stomachs and intestines of animals help with digestion.
Bacteria have enzymes that are able to digest tough foods, such as plant fibers, that animals are unable to digest. Bacteria also play a role in important ecological processes. They are one of the main players in the decomposition of dead plants and help to recycle nutrients back into ecosystems.
They are also able to take gases from the atmosphere and turn them into usable nutrients such as carbohydrates and nitrates. Certain industrial processes utilize the metabolism of bacteria. Bacteria are responsible for the fermentation that leads to the production of foods such as cheese and yogurt. Bacteria are also used in waste treatment facilities to help speed up the process of breaking down human waste, food waste and cleaning products.
Bacteria are found pretty much everywhere on Earth. Through the oceans, in soil, in air and inside other organisms. A large number of bacteria live on and within our very own bodies. They are in our stomachs and intestines, and our throats, ears and nose. They can also be found on our skin and hair. Bacteria can be literally be found everywhere.
Bacteria are prokaryotic organisms. Instead of having their DNA enclosed in a nucleus, the DNA is tightly coiled into a region of the cell called a nucleoid. A key feature of bacteria cells is a cell wall. The cell wall surrounds a bacteria cell and provides protection. It also maintains the shape of the cell and prevents it from bursting open. Compared to the cell walls of plants which are made from cellulose, bacteria cell walls have multiple layers of made from different compounds.
Different species of bacteria have cell walls with different structural make up. Differences in the structure of cell walls is what separate bacteria into gram-positive and gram-negative bacteria. It is the cell wall that is often targeted by antibiotics to kill bacteria. These hazards could destroy an entire colony. In order to avoid such perils, bacteria can become more genetically varied through recombination. Recombination involves the transfer of genes between cells.
Bacterial recombination is accomplished through conjugation, transformation, or transduction. Some bacteria are capable of transferring pieces of their genes to other bacteria that they contact. During conjugation, one bacterium connects itself to another through a protein tube structure called a pilus. Genes are transferred from one bacterium to the other through this tube. Some bacteria are capable of taking up DNA from their environment. These DNA remnants most commonly come from dead bacterial cells.
During transformation, the bacterium binds the DNA and transports it across the bacterial cell membrane. Transduction is a type of recombination that involves the exchange of bacterial DNA through bacteriophages.
Bacteriophages are viruses that infect bacteria. There are two types of transduction: generalized and specialized transduction. Once a bacteriophage attaches to a bacterium, it inserts its genome into the bacterium. The viral genome, enzymes, and viral components are then replicated and assembled within the host bacterium. Once formed, the new bacteriophages lyse or split open the bacterium, releasing the replicated viruses.
During the assembling process, however, some of the host's bacterial DNA may become encased in the viral capsid instead of the viral genome. When this bacteriophage infects another bacterium, it injects the DNA fragment from the previously infected bacterium. This type of transduction is called generalized transduction. In specialized transduction, fragments of the host bacterium's DNA become incorporated into the viral genomes of the new bacteriophages.
0コメント