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The good or the bad? • Microbes are normal We live with microbes all the time. These microbes are our normal flora. They are on our skin and inside our gut. They don’t usually cause disease and they can even help to protect us from infection by harmful microbes. Harmful, disease-causing microbes are called pathogens. Heath and disease • Good health is priceless. Bad health can mean poor quality of life and a shorter lifespan. So why are some people unhealthy? There can be many different reasons, including lifestyles and accidental injuries. We are going to look at one important cause of disease: infection by microbes. What are microbes? Microbes may be divided into three areas; • Virus • Bacteria • Fungi Viruses • Virus particles are tiny: about 0.00002 to 0.0003mm. • They are not complete cells but consist only of a protein coat surrounding genetic material, DNA or RNA. • Viruses always reproduce inside other cells, which are usually killed in the process. The ringworm fungus. DNA Protein coat End-plates Examples of illness which viruses cause • • • • • • • HIV smallpox the common cold Chickenpox Influenza Shingles Polio herpes, rabies Bacteria Ranging from 0.0001 to 0.02mm in length, bacteria are the smallest form of life that can live independently. They are single-celled: each cell is a separate working unit. There are two main shapes for bacteria: round (e.g. streptococcus) or rod shaped. Bacteria tend to be round or rod shaped. Rod Shaped Round shaped Illness which bacteria cause.. • • • • • • Salmonella Infections pneumonia meningitis ringworm and athlete's foot food-poisoning. Fungi • Yeasts and moulds are both examples of fungi. Yeasts are single-celled, often growing on rotten fruit and cause fermentation. They vary in size, but are big enough to see without a microscope. • There are many different sorts of protozoa. They all live in wet environments. Most can move around. • They vary in size from 0.01 to 0.2mm. Some protozoa, such as amoebae, cause a serious gut disorder called dysentery. Bacteria and reproduction • Bacteria are all around us. Given good growing conditions, a bacterium grows slightly in size or length, a new cell wall grows through the centre forming two daughter cells, each with the same genetic material as the parent cell. If the environment is optimum, the two daughter cells may divide into four in 20 minutes. If they divide so quickly then …. • Then why isn't the earth covered with bacteria? • The primary reason may be that conditions are rarely optimum. Scientists who study bacteria try to create the optimum environment in the lab: culture medium with the necessary energy source, nutrients, pH, and temperature, in which bacteria grow predictably. Are microbes/bacteria good or bad? Bacillus thuringiensis (bah-sill-us therin-gee-in-sis): a.k.a "Bt", a common soil bacterium. Wanted as a natural pest-killer in gardens and on crops . Streptomyces (strep-toe-myseas): soil bacteria wanted for making streptomycin, an antibiotic used to treat infections. • Pseudomonas putida (sue-doe-moanus poo-tea-dah): one of many microbes wanted for cleaning wastes from sewage water at water treatment plants. Friend or foe? • There are many other important jobs microbes do. They are used to make medicine. • They break down the oil from oil spills. They make about half of the oxygen we breathe. • They are the foundation of the food chain that feeds all life on earth. • In short, microbes are much more our friends than our enemies.