Basic techniques of microbiology
Dr Fairol give some briefing and explanation about the experiment 12 and experiment 13. My first thought about this experiments especially experiment 12 is I cannot understand the steps after Encik Zainuddin gave some demo then only I can understand so far. I asked my demo for my further understanding. On wednesday, as usual we observe the agar plate and record the reading of optical density using spectrophotometer.
Experiment 12: Nutritional requirements: Media for the routine cultivation of bacteria
To satisfy the diverse nutritional needs of bacteria, bacteriologists employ two major categories of media for routine cultivation. Chemically Defined Media are composed of known quantities of chemically pure, specific organic and/or inorganic compounds. Their use requires knowledge of the organism's specific nutritional needs. Chemical defined media which are inorganic synthetic broth and glucose salts broth. Inorganic synthetic broth is inorganic medium is prepared by incorporating the following salts per 1000 ml of water which are sodium chloride is 5 g, magnesium sulfate is 0.2 g, ammonium dihydrogen phosphate is 1.0 g, dipotassium hydrogen phosphate is 1.0 g and atmospheric carbon doixide. Glucose salts broth is composed of salts incorporated into the inorganic synthetic broth medium plus glucose, 5 g per liter, which serves as the sole organic carbon source. Complex media is the exact chemical composition of these media is not known. They are made of extracts of plant and animal tissue and are variable in their chemical composition. Most contain abundant amino acids, sugars, vitamins, and minerals; however the quantities of these constituents are not known. They are capable of supporting the growth of most heterotrophs. Complex media which is nutrient broth and yeast extract broth. Nutrient broth is basic complex medium is prepared by incorporating the following ingredients per 1000 ml of distilled water which is peptone is 5.0 g and beef extract is 3.0 g. Yeast extract broth is composed of the basic artificial medium ingredients used in the nutrient broth plus yeast extract, 5 g per liter, which is a rich source of vitamin B and provides additional organic nitrogen and carbon compunds. Measuring turbidity, we can evaluate the abilities of media to support the growth of different species of bacteria and nutritional needs of the bacteria. We can observe the amounts of growth, measured by turbidity, present in each culture following incubation.
Experiment 13: Use of Differential, selective and enriched media
Isolation of bacteria is accomplished by growing ("culturing") them on the surface of solid nutrient media. Such a medium normally consists of a mixture of protein digests (peptone, tryptone) and inorganic salts, hardened by the addition of 1.5% agar. Examples of standard general purpose media that will support the growth of a wide variety of bacteria include nutrient agar, tryptic soy agar, and brain heart infusion agar. A medium may be enriched, by the addition of blood or serum. Examples of enriched media include sheep blood agar and chocolate (heated blood) agar. Selective media contain ingredients that inhibit the growth of some organisms but allow others to grow. Selective media which is phenylethyl alcohol agar, crystal violet agar and 7.5% sodium chloride agar. For example, mannitol salt agar contains a high concentration of sodium chloride that inhibits the growth of most organisms but permits staphylococci to grow. Differential media contain compounds that allow groups of microorganisms to be visually distinguished by the appearance of the colony or the surrounding media. Differential/Selective media which is mannitol salt agar, MacConkey agar and eosin-methylene blue agar. Enriched media are media that have been supplemented with highly nutritious materials, such as blood, serum or yeast extract, for the purpose of cultivating fastidious organisms. Blood agar is one type of enriched media, allowing bacteria to be distinguished by the type of hemolysis produced. Hemolysis which is gamma hemolysis, alpha hemolysis and beta hemolysis.
Eosin-methylene blue agar of Escherichia coli, Enterobacter aerogenes, Salmonella typhimurium and Staphylococcus aureus
Microbiology week 9 (Fungi)
Characteristics of fungi
- multicellular and multinucleated (except
yeast) yeast is unicellular
- spore-bearing organisms
- chemoorganoheterotrophs with
absorptive metabolism
- saprophytes - osmotrophy
- no chlorophyll
- rigid cell wall chitin
- primary storage of p/s: glycogen
-Reproduce sexually and asexually
- are stationary organisms disperse by wind,
water and animals
Fungal Distribution and Importance
-Primarily terrestrial, few aquatic
-Primarily terrestrial
-Many are pathogenic in plants or animals
-Industrial importance
-Research use
Fungal Structure
• Cell walls composed of chitin polysaccharide
• Single-celled microscopic fungi = yeasts
• Body/vegetative structure of a fungus = thallus (pl. thalli) – multicellular fungi are called molds – thallus consists of long, branched hyphae filaments tangled into a mycelium mass
Feeding forms of fungi
• Saprobic heterotrophs – feed on dead or decaying organic matter
• Parasitic heterotrophs – feeding on living host at cost to the host
• Mutualistic heterotrophs – feeding of or with a living host without damaging the host, both host and fungus benefit
Fungal Reproduction
Asexual reproduction
– Parent cell undergoes mitosis to form daughter cells
– Mitosis in vegetative cells may be concurrent with budding to produce a daughter cell
– May proceed through a spore form
Sexual reproduction
– Involves fusion of compatible nuclei
• Homothallic: Sexually-compatible gametes are formed on the same mycelium (self-fertilizing)
• Heterothallic: Require outcrossing between different, yet compatible mycelia
– A dikaryotic stage can exist temporarily prior to fusion of two haploid nuclei
Sexual spores (Types)
• Zygospore - large spore enclosed in a thick wall.
• Ascospore - produce in a sac like structure called ascus.
• Basidiospore - formed externally at a base of basidium.
Life cycle
• Filamentous fungi can reproduce asexually by fragmentation
• Sexual and asexual reproduction- occurs by formation of spores
• Fungi are classified and identified by spore type
• Fungus spores and bacterial spore are different
• Spores are formed from the aerial mycelium
TYPES OF FUNGI
• Chytridiomycota
• Zygomycota
• Ascomycomycota
• Basidiomycota
• Microsporidia
Chrytridiomycota (Anaerobic Rumen Fungi)
• Neocallimastigales
• Obligate anaerobes
• Decompose cellulose
• Breakdown lignin deposits into smaller pieces
Phylum Zygomycota
• Terrestrial – decomposers – mutualists: mycorrhizae
• Form coenocytic hyphae containing numerous haploid nuclei
• Form zygosporangia – dikaryotic, resistant stage
• Bread Mold, Rhizopus stolonifer
• foods, antibiotics and other drugs, meat tenderizer, and food coloring
Phylum Ascomycota
-Sac fungi
-red, brown, and blue-green molds cause food spoilage
-some are human and plant pathogens
-some yeasts and truffles are edible
-some used as research tools
Basidiomycota
• Basidiomycetes (club fungi) – examples include rusts, shelf fungi, puffballs, toadstools, mushrooms – sexual reproduction form basidium
• basidiospores are released at maturity
Human Impact Basidiomycota
• Decomposers
• Edible and non-edible mushrooms – toxins are poisons and hallucinogenic
• Pathogens of humans, other animals, and plants
Microsporidia
• Obligate intracellular fungal parasites that infect insects, fish, and humans – Aquatic birds are common hosts and contribute to large numbers of spores in environment
• Transitional form is a spore structure capable of surviving outside the host
• Structurally similar to ‘classic’ fungi – contain chitin, trehalose, and mitosomes – however, lack mitochondria, peroxisomes and centrioles – unique morphology is polar tube essential for host invasion
Mycorrhizae
- Mutualistic association (plant root and fungi)
- Benefits for plants: increase surface area and increase the growth potential
- Benefit for fungi: feeding from tissues of the plant
- Mycorrhizal fungi : truffles, Auricularia
Lichens
• Mutualistic relationship between algae (or cyanobacteria) and fungi
• The algae produces food and the fungus portion provides protection, water, and minerals.
• Lichens may grow in extreme conditions (ex. Arctic areas too cold for most plants)
• Lichens are sensitive to environmental toxins, so they serve as indicators of the ecological health of an area.
Ecological impact of fungi
•Fungi as decomposers
•Fungi to modify habitat
•Fungi as spoilers
•Fungi to improve plant growth
•Fungi as food
•Fungi as pathogens
Yeast
Non filamentous
• Unicellular
• Typically spherical or oval
• Fission yeast – divide evenly to produce new cells
• Budding yeast – divide unevenly
• Yeast are capable of facultative anaerobic growth
• Baking
• Fermenting alcoholic beverages – Beer, wine, distilled spirits
• Model organism in cell biology research
• Microbial fuel cells
• Opportunistic pathogens
• Saccharomyces carlsbergensis (pastorianus)
• Brettanomyces (wild yeast)
• Bioremediation
• Yarrowia lipolytica is known to degrade palm oil mill effluent, TNT and other hydrocarbons such as alkanes, fatty acids, fats and oils
Dimorphic Fungi
• dimorphism- two forms of growth
• either as mold or yeast
• Mold-like (vegetative and aerial hyphae)
• Yeast-like (reproduce by budding)
• temperature dependent (37°C, yeast-like; 25°C, mold-like), Carbon dioxide dependent.
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