Basic techniques of microbiology
Dr Fairol give some briefing and explanation about the experiment 14 and experiment 15.On tuesday, we did the experiment 14 using agar plate and Sabouraud broth tubes containing inverted Durham tubes and 15 using soy broth (TSB) tubes. On wednesday, we observe the agar plate and the absorbance reading of spectrometer.
Experiment 14: Physical Factors: Temperature
Microbial growth is directly dependent on how temperature effects cellular enzymes. With increasing temperatures, enzyme activity increases until the three-dimensional configuration of these molecules is lost because of denaturation of their protein structure. As the temperature is lowered toward the freezing point, enzyme inactivation occurs and cellular metabolism gradually diminishes. At 0°C, biochemical reactions cease in most cells. Bacteria, as a group of living organisms, are capable of growth within an overall temperature range of minus 5°C to 80°C. Each species, however, requires a narrower range that is determined by the heat sensitivity of its enzyme systems.
Minimum growth temperature:
The lowest temperature at which growth will occur. Below this temperature, enzyme activity is inhibited and the cells are metabolically inactive so that growth is negligible or absent.
Maximum growth temperature:
The highest temperature at which growth will occur. Above this temperature, most cell enzymes are destroyed and the organism dies.
Optimum growth temperature:
The temperature at which the rate of reproduction is most rapid; however, it is not necessarily optimum or ideal for all enzymatic activities of the cell.
Psychrophiles
Bacterial species that will grow within a temperature range of -5°C to 20°C. The distinguishing characteristics of all psychrophiles is that they will grow between 0 degree celsius and 5°C.
Mesophiles
Bacterial species that will grow within a temperature range of 20°C to 45°C . The distinguishing characteristics of all mesophiles are their ability to grow at human body temperature (37°C) and their inability to grow at temperatures above 45°C. Mesophiles with optimum growth temperature between 20°C and 30°C are plant saprophytes. Mesophiles with optimum growth temperature between 35°C to 40°C are organisms that prefer to grow in the bodies of warm-blooded hosts.
Thermophiles
Bacterial species that will grow at 35°C and above. Facultative thermophiles is organisms that will grow at 37°C, with an optimum growth temperature of 45°C to 60°C. Obligate thermophiles is organisms that will grow only at temperatures above 50°C, with optimum growth temperatures above 60°C.
Sabouraud broth tubes containing inverted Durham tubes of Saccharomyces cerevisiae in 20°C
Trypticase soy agar plates of Escherichia coli, Bacillus stearothermophiles, Pseudomonas aeruginosa and Serratia marcescens at 4°C
Experiment 15: Physical Factors: pH of the extracellular environment
Growth and survival of microorganisms are greatly influenced by the pH of the environment, and all bacteria and other microorganisms differ as to their requirements. Based on their optimal pH, microorganisms may be classified as acidophiles, neutrophiles or alkalophines. Each species has the ability to grow within a specific pH range; the range may be broad or limited, with the most rapid growth occurring within a narrow optimum range. These specific pH needs reflect the organisms' adaptations to their natural environment. For example, enteric bacteria are capable of survival within a broad pH range, which is characteristics of their natural habitat, the digestive system. Bacterial blood parasites, on the other hand, can tolerate only a narrow range; the pH of the circulatory system remains fairly constant at approximately 7.4.
Microbiology Week 10 (Protists)
Nutrition in Protists
• Protozoa are chemoheterotrophic protists
• Photoautotrophic protists
• Mixotrophic protists
Protist Morphology
- plasma membrane structure similar to multicellular plants/animals
- cytoplasm sometimes subdivided into outer gelatinous ectoplasm just underneath plasma membrane and inner fluid region termed endoplasm
- pellicle structure provides support
- vacuoles commonly present in protists
- energy production
- cilia/flagella may be present for motility/feeding
Protozoa
Different from prokaryotes-- relatively larger and
eukaryotic nature
Different from algae -- no chlorophyll
Different from yeast and fungi--by their motility and
lack of cell wall
Different from slime molds--lack of fruiting body
Unicellular, eukaryotic animal-like protists
Predatory or parasitic
Some are pathogenic
Aerobic, anaerobic chemoheterotrophic organism
Colorless and motile
Reproduction
-Asexually by fission, budding, multiple fission (schizogony)
-Sexual reproduction is conjugation/produce gametes.
Found in water and soil.
Some are part of the normal flora of animals
Nutrition of protozoa
Mostly aerobic heterotrophs, some are capable of anaerobic growth.
Dinoflagellates and Euglenoids are capable of photosynthesis
Obtain food through:
-Ingestion/swallowing of particulate or whole bacteria via gullet/cytostome
-Pinocytosis - fluid sucked into a channel
-Phagocytosis - surrounding the food particle with their flexible cell membrane
-Absorption - through plasma membrane
Archaezoa
• flagellated
• two or more flagella
• move in whiplike manner
• free-living
• parasitic/pathogenic
• Freshwater
• Trypanosoma gambiense
• African sleeping sickness-in human
• Lives and grow in the blood stream– inflammation of the brain and spinal cord
Rhizopoda
• Amoebas
• move by pseudopods- ameboid movement
• phagocytosis- obtain food
• habitat-freshwater, marine
• cause amoebic dysentery – human
• Transmitted from person to person in the cyst form – fecal contamination
• eg. Amoeba proteus, Entameoba histolytica
CILIOPHORA (ciliates)
• possess cilia
• 2 kind of nuclei
• Micronucleus - inheritance and sexual reproduction
• Macronucleus - production of mRNA
• best known - Paramecium
• presence of gullet (mouth)/cystostome - ingesting particulate material
• habitat- freshwater, marine
• Balantidium coli - human parasite - Dysentery
APICOMPLEXA
• not motile in mature forms.
• obligate parasites.
• food are absorbed through the outer wall.
• complex life cycle - transmission between several hosts.
• primarily animal parasites, insects.
• Plasmodium vivax - causing Malaria.
• Toxoplasma - causing toxoplasmosis.
Algae
– They have a simple morphological construction
– Naked reproduction structures - asexual (all) and sexual (some)
– Mostly photoautotropic
– Contain chlorophyll a and other pigment
– Requires water
– Found virtually in any habitat on earth
– Classified according to thei rRNA sequences, structures, pigments and other qualities.
Habitat
• aquatic habitat- fresh water, marine and brackish
• moist soils and artificial aquatic habitat (fish tanks, pool)
• few in dry soils
• acidic habitat
Motility of Algae
• If motile, due to flagella:
• Single flagella—Euglena
• Two or 4 polar flagella- Chlorophyta
• Two flagella of different length and point of insertion—Dinoflagellates
• Most cases, non-motile in vegetative stage and form mo)le gametes only during sexual reproduction
Distribution of Algae
- Planktonic
- Benthic
- Neustonic
Chlorophyta
• Green algae
• Cellulose cell walls
• Unicellular or multicellular
• Chlorophyll a and b
• Store glucose polymer
• Gave rise to terrestrial plants
Rhodophyta
• reddish colour
• delicately branch thalli
• Chlorophylls a and d, phycocyanin, phycoerythrin
• red pigment absorb blue light
• mostly multicellular
• cell wall- cellulose/agar
• sexual reproduction
• storage material- glucose polymer
• habitat- marine (greater ocean depths)
Phaeophyta
• brownish colour
• macroscopic
• Chlorophylls a and c, xanthophylls
• multicellular
• cell wall- cellulose/algin
• sexual reproduction
• storage material- carbohydrate
• habitat- marine (coastal water)
Chrysophyta (Diatoms-Bacillariophyta)
• golden-brown algae
• produce domoic acid- domoic acid intoxication
• Chlorophylls a, and c,
• unicellular
• cell wall- peptin and silica
• sexual reproduction
• storage material- oil
• habitat- fresh water, marine, soil
• Important in global carbon cycling – marine planktonic diatoms produce 40–50% of organic ocean carbon
Phyrrophyta (Dinoflagellata)
• unicellular plankton
• brownish
• 2 flagella in perpendicular opposing grooves
• Some produce neurotoxins
• can cause ‘red tides’- gives ocean a deep red colour
• Chlorophylls a and c
• cell wall- cellulose
• storage material- starch
• habitat- freshwater, marine
Euglenophyta (also considered with the protozoa)
• unicellular flagellated
• green colour
• Chlorophylls a and b, carotene
• can spontaneously lost chlorophyll (dark)- heterotrophic organism
• cell wall- none
• rigid plasma membrane-pellicle
• no sexual reproduc0on
• storage material- glucose polymer
• habitat- freshwater, a few marine
Slime Molds
- Resemble fungi in appearance and life-style
- Different in cellular organiza)on, reproduc)on and
life cycles
- Three divisions
a) Myxomycota (Plasmodial slime molds)
b) Acrasiomycota (Cellular slime molds)
c) Peronosporomycetes (Water molds)
Myxomycota
- plasmodial (acellular) slime molds
- glistening, viscous masses of slime
- saprophytes
- multinucleated
- motile amoeboid mass called plasmodium (lack of
cell wall)
- phagocytosized dead material
Acrasiomycota
- individual amoeboid cells (unicellular)
- feed phagocytically
-
plentiful of food, divide by mitosis and
cytokinesis
- Cellular slime molds
– great interest to cell and developmental
biologists
– provide a comparatively simple and easily
manipulated system
– for understanding how cells interact to
generate a multicellular organism
Peronosporomycetes
• “Egg fungi” formerly called oomycetes are
diploid and no chitin in cell wall
• Some grow in cottony masses on dead algae
and animals
• Some parasites of fish gills
• Plant diseases include blue mold on tobacco
and Irish potato blight
Distribution and functions of molds:
- Moist terrestrial habitats e.g. soil, decaying wood, dung
and etc.
- Engulf bacteria (as predator)
- As decomposer and consumer in the ecosystem
- Recycling of nutrients (regenerate consumer’s waste,
allowing plants to reuse nutrients)
- Cause diseases in plants e.g. tobacco plants, potatoes,
grapes
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