Introduction to Microbiology Summary Notes PDF

**Introduction to Microbiology** **Summary Notes** **Why are microorganisms important?** **Micro-organisms are typically known for causing diseases that make people ill. However, most microorganisms are beneficial!!** - **They decompose plant and animal remains & recycle nutrients to the s...

**Introduction to Microbiology** **Summary Notes** **Why are microorganisms important?** **Micro-organisms are typically known for causing diseases that make people ill. However, most microorganisms are beneficial!!** - **They decompose plant and animal remains & recycle nutrients to the soil** - **They are important ecologically in food chains** - **They are used as foods (eg mushrooms) or in the production of foods (eg bread, yoghurt, cheese, beer & wine)** - **Microorganisms can form beneficial associations with plants and animals. Eg. our normal flora is important in preventing disease causing microbes populating on our body or gut bacteria assist in digestion** - **They are used in industrial production of drugs (eg some antibiotics) & other useful chemicals (eg food additives) and tools in science research (eg molecular biology)** **Please watch this video that introduces microbiology: ** **Structure of Typical Bacteria** (Lee & Bishop (2016) page 46) Please watch this short video for a description of bacteria: **Bacterial Cell Wall** (Lee & Bishop (2016) page 48) - Provides mechanical support to the bacterial cell so the cell does not burst when water moves into the cell. - Major component of the cell wall is **peptidoglycan** (sugars). - Based on the composition of the bacterial cell wall, bacteria can be classified into one of two major groups - **gram positive or gram negative**. - Staining process results in gram positive bacteria staining purple and gram-negative bacteria staining pink/red. - **Gram positive** bacteria possess a cell wall that consists of a **thick peptidoglycan layer**. - **Gram negative** bacteria possess a cell wall that consists of a - **thin peptidoglycan** and - an **additional outer membrane layer** (serves as a barrier from entry of some antibiotics or destructive enzymes). Outer membrane contains specific lipids that are toxic to the infected host (eg cause fever or shock) - Certain antibiotics are ineffective on gram negative bacteria due to the inability to penetrate the outer membrane layer.  **Endospores -** feature that assists bacterial survival (page 51) - Some bacteria are able to produce spores when the environmental conditions become unfavourable. - Endospores are surrounded by a spore coat to provide protection. - Endospores are highly resistant to destruction that would normally kill bacteria (eg boiling, freezing, exposure to chemicals or radiation). - Can remain dormant and viable for years **Reproduction of Bacterial Cells** (page 54-55) Bacteria reproduce by a process called **BINARY FISSION**. **Nomenclature of Bacteria** - **Microorganisms always have 2 names** - **The first name is the genus name The second name is the species name** - **Names are always written in italics (or underlined if hand-written)** - **Sometimes they are abbreviated eg *S. aureus, E. coli*** **What do bacteria require for growth? (Lee & Bishop (2016) page 52-55)** - **A supply of nutrients- need supply of carbon that they use to construct cellular parts.** - **Suitable environmental conditions** i. **Temperature - influences reproduction rates. Slower in lower temperatures. Pathogenic bacteria have optimal temperature of 37°C.** ii. **Oxygen - some bacteria require oxygen for survival while other bacteria survive in oxygen poor conditions** iii. **pH - most survive in neutral pH.** iv. **Moisture- require water for reproduction.** **Shapes of Bacteria** **Bacteria come in a range of shapes and sizes.** **Coccus (plural: cocci)- spherical shape** **Staphylococci - clusters of round spheres** **Streptococci - chain of round spheres** **Bacillus (plural: bacilli) - rod shaped** **Vibrios- curved, rod shaped** **Spirilla- spiral shaped** **Viruses** **Structure of a virus** (Lee & Bishop (2016) page 86) - Smaller than bacteria. Not visible with light microscope. - Nuclear material encased in a **capsid** (protein coat). - Some viruses have an additional outer coating called an **envelope**. - Envelope is similar to cell membrane of host cell. - Spikes present on envelope to assist in attachment to host cell. - No ribosomes or organelles. - Not considered to be living as unable to carry out any metabolic activities or reproduce outside of a host cell. - Only able to reproduce inside a host cell. - Shape and structure can vary ( see page 87) and is used to classify virus.  **How do viruses replicate?** (Lee & Bishop (2016) page 91) 1. **Attachment-** of virus to host cell (eg, human cell) 2. **Penetration-** of virus or nuclear material into the host cell 3. **Uncoating** - removal of the capsid to release the viral nuclear material into the cytoplasm of the host cell 4. **Synthesis** - viral nuclear material (nucleic acid and proteins) is replicated by the host cell 5. **Assembly** - newly synthesised viral nuclear material and protein coating are assembled to form new viruses. 6. **Release** - Viruses are released from host cell by rupturing the cell (resulting in death of host cell) or budding from cell membrane. (Release or lysis) Viral replication. **Fungi** (Lee & Bishop (2016) page 112) - Wide range of fungi found in nature. - **Yeasts**- unicellular, usually spherical or oval in shape. - **Moulds**- filamentous, multicellular- eg mushrooms - Small number are human pathogens. **Structural features** - Nucleus present - cell organelles present - Cell structures similar to human cells - Fungi have a cell wall- animal cells do not have a cell wall. - Different to plants as fungi do not contain chlorophyll (responsible for usually making plants green). - Many fungi can grow in environments with low moisture and low pH. Fungi are able to survive in environments that bacteria can-not. - Fungi are slightly larger in size than bacteria. - Human fungal infections are typically localised to the skin or mucosa and so do not cause severe illnesses. However when fungal infections become systemic (spread through the body), they can become life-threatening. - Examples- *Tinea pedis* (athletes foot); *Candida albicans* (thrush) - Some fungi cause infections when host defences are weakened (eg immunosuppressed, transplant patients) or balance of microbial flora becomes disrupted. - Example *C.albicans* can become pathogenic (and develop into thrush) if female host takes prolonged antibiotics, that destroy the naturally existing species of *Lactoacillus* in the vaginal (that is responsible for maintaining the acidic vaginal environment). The change is pH of the vaginal environment creates an ideal opportunity for the *C.albicans* to populate and cause thrush. **Reproduction of fungi** - Yeasts reproduce by a process called **budding**. - The cell will produce an outgrowth, which gradually increases in size. The enlarged region eventually separates from the main cell forming a daughter cell that is identical to the original cell. http://www.fungionline.org.uk/images/1intro/yeast1.JPG - Moulds reproduce by **spores**. The spores are released into the air and spread by air currents. **Protozoa** (Lee & Bishop (2013) p 121) - Single cell eukaryotic organisms. - Mostly found in water habitats, but some exist as parasites in animals and insects. - Most do not cause serious illness to humans. - Capable of forming **cysts** - cells surrounded by a protective layer that is resistant to drying- capable of surviving for long periods. - Examples of diseases caused by pathogenic protozoa include Giardiasis (caused by *Giardia intestinalis*) and Malaria (caused by *Plasmodium* species).  **Prions** (Lee & Bishop (2013) p 530) - Not a cellular micro-organism. Prion is a mutated protein. - Mutation of the normal protein into an abnormal form (called prion). - Function of the normal protein is unknown, however mutated form causes prion disease. - Abnormal protein accumulates in brain tissue causing degeneration of the nervous tissue. Results in deterioration of muscle and dementia-like symptoms with eventual death within one year. - Caused \'Mad Cow\' disease in UK.