Monera.docx

Monera (Bacteria) Structure of Bacterial Cell (1) - Cell Wall: Made of sugars and protein. Its purpose is to protect the bacteria from mechanical damage and osmotic rupture - Plasmid: Found in the cytoplasm. Contain genetic information. Plasmids replicate inside a bacterium - Nucleoid: Contains the...

Monera (Bacteria) Structure of Bacterial Cell (1) - Cell Wall: Made of sugars and protein. Its purpose is to protect the bacteria from mechanical damage and osmotic rupture - Plasmid: Found in the cytoplasm. Contain genetic information. Plasmids replicate inside a bacterium - Nucleoid: Contains the genomic DNA - Ribosomes: Protein synthesis Sometimes Present - Flagellum: Allow the bacteria to move - Slime capsule: Protects the bacteria from phagocytic white blood cells Bacteria are classified as prokaryotes for the following reasons; - They do not have a nuclear membrane - They do not have membrane-bound organelles Bacterial Shapes - Spheres (cocci): Can occur singularly or in various groupings - Rods (bacilli): Occur singularly or in various groups. Some have flagella - Spirals (spirillum): Some are tightly coiled while others are only slightly coiled. Some have flagella (2) Reproduction in Bacteria Asexual reproduction by a process called binary fission. In binary fission, the genetic material and plasmids replicate and then move to either side of the midline of the bacteria. The bacteria then pinches in its cell membrane and the cell wall grows across the middle, producing two identical cells. Under ideal conditions, such species such as E.coli, can reproduce every 20 minutes. However, such rates of multiplication are difficult to sustain. (3) Bacterial Growth Phases 1. Lag phase – In the lag phase, the bacteria are adjusting to their surroundings and preparing to undergo reproduction 2. Log phase – Reproduction begins in the log phase, and since resources ae plentiful, it is possible for the population to grow exponentially 3. Stationary phase – Competition occurs in the stationary phase as resources are now in limited supply, and death rate equals reproductive rate. Conditions are no longer ideal due to the build up of waste materials 4. Death or decline phase – Toxic waste is so concentrated that the death rate exceeds reproductive rate (4) Endospores When a bacterium is exposed to harmful conditions, it responds by forming a resistant structure called an endospore. The process of endospore formation; - The DNA replicates and the new DNA moves to one end of the cell - A thick, resistant wall then surrounds the new DNA - The contents of the endospore shrink as water is removed and its metabolism stops - The original cell bursts, releasing the endospore (5) Temperatures more than 120oC are required to kill endospores. Endospores can remain viable for centuries, becoming active only when suitable conditions are encountered. Nutrition Bacteria can be divided into two main groups; 1. Autotrophic – make their own food a. Photosynthetic – Have the ability to make their own food by photosynthesis, using sunlight as their source of energy b. Chemosynthetic – Obtain their energy from other chemical reactions and not light 2. Heterotrophic – obtain their food from other organisms a. Saprophytic organisms – live by digesting dead organic material and this causes the material to decay. In the process, valuable nutrients are returned to the environment and made available for use by other organisms b. Parasitic bacteria – Live in or on another species and cause them harm. They are responsible for many human, animal, and plant diseases Factors affecting growth - Temperature: Most mammalian bacteria function best at around 35 – 40oC. Cultures must be kept at this temperature to ensure maximum growth - pH: Most bacteria function best at around pH 7. Bacterial enzymes are denatured in an unsuitable pH - Oxygen concentration: Most bacteria are anaerobic, so keeping oxygen out of their environment is important - Availability of nutrients: An excess of nutrients must be kept available at all times to supply all the materials for growth and reproduction - Availability of water: Water is essential for bacterial growth. If water is removed by drying or osmosis, the bacteria will die - Waste materials: Waste materials must be removed to prevent a build up of toxic substances that would otherwise inhibit growth Antibiotics Antibiotics are substances made by microorganisms that kill microorganisms. The ability to kill microorganism allows antibiotics to be used to control pathogenic (disease causing) organisms, such as tuberculosis and thrush. Most antibiotics work by inhibiting cell wall synthesis during cell division e.g., penicillin. Antibiotic Resistance Antibiotic Resistant means not killed by antibiotics. There are three main causes of antibiotic resistance; - Overuse: Taking antibiotics for the common cold or flu. Antibiotics do not kill viruses. - Failure to complete the course: If a person stops taking an antibiotic before the course is finished, it gives resistant bacteria the chance to multiply. This means that infection can re-occur and will be much harder to treat as the bacteria are now more resistant to the antibiotic. - Antibiotic residues in food: Antibiotics are given to farm animals to treat infection and to make them gain weight faster. If this is done too close to slaughter, traces of the antibiotic will remain in the meat and be passed on in the food chain. Economic Importance of Bacteria Beneficial Bacteria - Production of yoghurt and cheese using Lactobacillus - Manufacture of antibiotics e.g., penicillin - Bacteria are used to bread down dead plants and animals which leads to nutrient recycling in soil Harmful Bacteria - Bacteria can cause human disease e.g., TB, meningitis, typhoid, pneumonia - Food spoilage e.g., Lactobacilli causes milk to turn sour Bioprocessing Bioprocessing is the use of organisms or their products to make useful substances. There are two standard processes to do this; 1. Batch Process A fixed amount of nutrients and microorganisms are added to the bioreactor at the start. Air is added if needed and waste gases are removed. Growth is allowed up to a certain point, the bioreactor is emptied, and the product is extracted. The bioreactor is cleaned and sterilised. Used for antibiotics. (6) 2. Continuous process Nutrients are continuously added to the bioreactor. Once the bioreactor is set up, spent medium and products are continuously removed. This is a quicker process because there is no need to empty the bioreactor regularly. It also allows for a continuous yield of product. By adjusting the nutrients added, the growth rate can be kept at a level which gives the maximum yield of product. Used for single-celled proteins.