microorganism/microbiology/pathogens.pptx

for learning the basics about microorganism and microbiology

1. BY Dr. S. HIMALINI

2. Microorganisms (Microbes) :-   Very small organisms which cannot be seen with the naked eye. may be unicellular or multicellular may exist alone like amoeba or in colonies like Fungi & Bacteria found in all kinds of environment like ice cold climate, hot springs, deserts, marshy lands etc. They are also found inside the bodies of other organisms

3. Types of microorganisms :-

4. They are different from other microorganisms as they  reproduce only in the body of host organisms like bacteria, plants or animals. Virus

5. Friendly microorganisms   a)Making curd from milk :- The bacterium called Lactobacillus reproduces in milk and helps to convert milk into curd. b) Making bread :- The fungus called yeast reproduces in flour dough and produces carbon dioxide during respiration which makes the dough soft and helps in making bread, cakes, biscuits, pastries etc. c) Making alcohol :- Yeast is used for commercial production of alcohol & wine. The fungus called yeast reproduces in sugar solution and converts it into alcohol. This process is called fermentation. • Louis Pasteur discovered fermentation in 1857.

6. Increasing Soil Fertility  Some Bacteria and Blue Green Algae are able to fix nitrogen from the atmosphere to enrich soil with nitrogen and increase its fertility. These microbes are called Biological Nitrogen Fixers. d) Making medicines :- Some bacteria and fungi are used to make medicines which kill or stops the growth of disease causing microrganisms . Such medicines are called antibiotics. Eg :- streptomycin , tetracycline, erythromycin etc.

7. Cleaning the Environment  Micro organisms decompose dead organic waste of plants and animals and convert them into simple substances which are again used by other plants and animals.

8. Harmful microorganisms   Some micro organisms cause diseases in plants and animals. Such disease causing microorganisms are called pathogens. ii) Some micro organisms grow in food substances and produce toxic substances and makes the food poisonous. Food poisoning causes illness and even death. iii) Some microorganisms spoil materials like clothing, leather, wood etc.

9. Pathogens  Disease causing microorganisms. Enter our body through air, water, food, contact or insects. Diseases which can spread from an infected person to a healthy person are called communicable diseases. Eg :- cholera, common cold, chicken pox, tuberculosis etc. Some insects and animals act as carriers of disease causing microbes. Eg :- House fly, Female anopheles mosquito (malaria), Female aedes mosquito (dengue fever) etc.

10. Disease causing microorganisms in plants :-   Microorganisms cause diseases in plants like rice, wheat, potato, sugarcane, apple, orange etc. These diseases reduce crop yield. They can be controlled by using chemicals which kill the microbes.

11. Some common human diseases caused by microorganisms:-   Human disease Causative Mode of microorganism transmission Chicken pox Virus Air / Contact Polio Virus Air / Water Measles Virus Air Hepatitis – B Virus Water Tuberculosis Bacteria Air Typhoid Bacteria Water Cholera Bacteria Water / Food Malaria Protozoa Mosquito Some common plant diseases caused by microorganisms :- Plant disease Causative Mode of microorganism transmission Citrus canker Bacteria Air Rust of wheat Fungi Air / Seed Yellow mosaic of Okra (Lady’s finger) Virus Water bhindi

12. Some common plant diseases caused by microorganisms Food Poisoning  • Could be due to consumption of food spoilt by micro organisms • So it is important to preserve food. Food preservation   Chemical method : • Pickles can be preserved by using chemicals like salts and edible oils. Jams and squashes can be preserved by using sodium benzoate, sodium meta bisulphate These chemicals are called preservatives.

13. Salting   Food items like fish, meat, amla , raw mangoes, tamarind etc can be preserved by using common salt. It prevents the growth of microbes By using sugar   Food items like jams, jellies, squashes etc. can be preserved by using sugar solution. It reduces the moisture content which inhibits the growth of bacteria. By using Oil & Vinegar Prevents spoilage of pickles because bacteria cannot live in such an environment• Vegetable, Fruit, Fish and meat are often preserved by this method.

14. Surface Structures Flagella:  The flagella of motile bacteria differ in structure from eukaryotic flagella. A basal body anchored in the plasma membrane and cell wall gives rise to a cylindrical protein filament. The flagellum moves by whirling about its long axis. The number and arrangement of flagella on the cell are diagnostically useful. Pili ( Fimbriae ):   Pili are slender, hairlike , proteinaceous appendages on the surface of many (particularly Gram-negative) bacteria. They are important in adhesion to host surfaces.

15. Capsules :  Some bacteria form a thick outer capsule of high-molecular-weight, viscous polysaccharide gel; others have more amorphous slime layers. Capsules confer resistance to phagocytosis . Cytoplasmic Structures Plasma Membrane:  The bacterial plasma membrane is composed primarily of protein and phospholipid (about 3:1). It performs many functions, including transport, biosynthesis, and energy transduction.

16. Organelles:   The bacterial cytoplasm is densely packed with 70S ribosomes . Other granules represent metabolic reserves (e.g., poly- β- hydroxybutyrate , polysaccharide, polymetaphosphate , and metachromatic granules). Endospores :   Bacillus  and  Clostridium  species can produce endospores : heat-resistant, dehydrated resting cells that are formed intracellularly and contain a genome and all essential metabolic machinery. The endospore is encased in a complex protective spore coat.

17.  Fungus Fungi are eukaryotic cells, which contains similar organelles to human cells, these include: Ribosomes  – the same function are prokaryotic ribosomes but differ in size and structure. Mitochondria  – produce energy molecules for use in the metabolism. Endoplasmic reticulum  – involved in protein synthesis and protein transport. Nucleus  – a membrane-bound structure that encloses the genetic material of the cell. Nucleolus  – an area in the nucleus where ribosomes are assembled. Cell wall  – contains chitin and provides strength and structure to the cell. Cell membrane  – this is significantly different to the human cell membrane. It lies under the cell wall and encases the membrane. Golgi apparatus  – an organelle involved in targeting newly synthesized substances and proteins. Storage vacuole  – membrane-covered spaces within cells that store nutrients and waste products. Centrioles  – has a role in organizing the skeletal system of the cell.

18. Protozoan Protozoa are eukaryotes which possess many of the organelles similar to fungi. However, unlike fungi, protozoa do not have cell walls. Protozoa have a  pellicle , which is a very thin protein layer that protects the cell membrane.

19. Virus Viral structures are the most different to other microbe structures. Viruses can be naked and composed of the capsid and genetic material or be enclosed by an envelope. The particular virus structures are: Capsid  – a protein coat that encapsulates the nucleic acid of the virus. Nucleic acid  – the genetic material of the virus, can either be RNA or DNA and can also be single or double-stranded. Envelope  – external membrane which is typically a phospholipid bilayer and contains glycoproteins . Spike  – proteins on the outer surface of the envelope which can have multiple functions including adhering to surfaces.

20. Important Chemical Components of Surface Structures Cell Wall Peptidoglycans :   Both Gram-positive and Gram-negative bacteria possess cell wall peptidoglycans , which confer the characteristic cell shape and provide the cell with mechanical protection. Peptidoglycans are unique to prokaryotic organisms and consist of a glycan backbone of muramic acid and glucosamine (both N-acetylated), and peptide chains highly cross-linked with bridges in Gram-positive bacteria (e.g.,  Staphylococcus aureus ) or partially cross-linked in Gram-negative bacteria (e.g.,  Escherichia coli ). The cross-linking transpeptidase enzymes are some of the targets for b- lactam antibiotics.

21. Teichoic Acids Teichoic acids are polyol phosphate polymers bearing a strong negative charge. They are covalently linked to the peptidoglycan in some Gram-positive bacteria. They are strongly antigenic, but are generally absent in Gram-negative bacteria. Lipoteichoic Acids:   Lipoteichoic acids as membrane teichoic acids are polymers of amphiphitic glycophosphates with the lipophilic glycolipid and anchoAred in the cytoplasmic membrane. They are antigenic, cytotoxic and adhesins (e.g.,  Streptococcus pyogenes ).

22. Lipopolysaccharides :   One of the major components of the outer membrane of Gram-negative bacteria is lipopolysaccharide ( endotoxin ), a complex molecule consisting of a lipid A anchor, a polysaccharide core, and chains of carbohydrates. Sugars in the polysaccharide chains confer serologic specificity. Wall-Less Forms:   Two groups of bacteria devoid of cell wall peptidoglycans are the  Mycoplasma  species, which possess a surface membrane structure, and the L-forms that arise from either Gram-positive or Gram-negative bacterial cells that have lost their ability to produce the peptidoglycan structures.