Bacteria Notes:<\/p>\n
Part One: Unity and Diversity<\/p>\n
Ways to classify bacteria<\/p>\n
Shape and size
\nGram positive and Gram negative
\nMetabolism (include respiration and food source)
\nA. Size and Shape<\/p>\n
\u00b7 Bacteria were first described by Leeuwenhoek in 1677 after he had invented the compound microscope.<\/p>\n
\u00b7 Bacteria range in size from about 1 to 10 um long by about 0.2 to 0.3 um across (1 um = .001 mm).<\/p>\n
Most bacteria come in one of three different shapes:<\/p>\n
(1) Rod shaped: Bacillus(i) [filaments or single].<\/p>\n
(2) Spherical shaped: Coccus(i) [pairs, chains, groups or single].<\/p>\n
(3) Spiral shaped: Spirillum(a) [seldom in colonies]<\/p>\n
Some bacteria tend to form groups:<\/p>\n
Diplococci are pairs of spherical shaped bacteria<\/p>\n
Streptococci are chains of spherical shaped bacteria<\/p>\n
Staphylococci are clusters of spherical shaped bacteria<\/p>\n
B: Gram positive and Gram negative<\/p>\n
The term gram positive or negative, refers to both a staining proccess and specific structure of bacterial cell membranes or wall. The gram staining method is one of the more important techniques in microbiology. Yet one has to realize that this technique is not 100 percent fool proof. Differences in results can be due to type of stains and age of bacteria.<\/p>\n
The staining process follows the following protocal:
\nHeat fix bacteria to slide
\nStain with purple dye (crystal violet), rinse with distilled water
\nStain with with iodine (marker), rinse with water
\nRinse with alchol wash, functions as a decolorization process in which negative lose colour.
\nStain with safranin (red stain) which is counter stain for gram negative<\/p>\n
In regards to cell membrane structures:<\/p>\n
Gram positive bacteria have cell walls composed of peptidoglycan (murein) and teichoic acid. ( basically a sugar based structure combined with amino acids)<\/p>\n
Gram negative bacteria also have cell walls composed of a peptidoglycan ( in small amounts) but this layer is surrounded by a lipopolysaccharide outer membrane.<\/p>\n
Comparison of Characteristic of Gram + and Gram –<\/p>\n
Characteristic<\/p>\n
Gram Positive<\/p>\n
Gram Negative<\/p>\n
Gram Reaction<\/p>\n
Stain dark violet or purple<\/p>\n
Stain pink<\/p>\n
Ratio RNA to DNA<\/p>\n
8:1<\/p>\n
1:1<\/p>\n
Nutritional requirements<\/p>\n
More complex<\/p>\n
Less complex<\/p>\n
Susceptability to penicillin<\/p>\n
Marked<\/p>\n
Less marked<\/p>\n
Susceptability to streptomycin and tetracycline<\/p>\n
Much less<\/p>\n
Marked<\/p>\n
Susceptability to anionic detergents<\/p>\n
Marked<\/p>\n
Less marked<\/p>\n
Resistance to sodium azide<\/p>\n
Marked<\/p>\n
Less marked<\/p>\n
C: Metabolism and Nutrition<\/p>\n
Cell Metabolism:<\/p>\n
Nutrients are ingested and then:<\/p>\n
1. broken down by enzymes within cell<\/p>\n
2. further breakdown of material is done to produce energy<\/p>\n
\u00b7 Energy is absorbed by biochemical ADP (adenine di phosphate)<\/p>\n
\u00b7 Energy is released by biochemical ATP ( adenine tri phosphate)<\/p>\n
Energy can be produced with or without oxygen<\/p>\n
1. Anearobic: are bacteria that do not need oxygen for cell metabolism<\/p>\n
2. Areorobic: are bacteria that require oxygen for cell metabolism<\/p>\n
3. Facualtative: are bacteria that can metabolize with or without oxygen<\/p>\n
Obligate Aerobes are those which must have oxygen
\nObligate Anaerobes are bacteria which cannot tolerate oxygen.
\nThere are many types of nutrition found among bacteria:<\/p>\n
Autotrophic Nutrition:<\/p>\n
1. Some are photosynthetic (use sunlight energy to produce their own food).<\/p>\n
2. Some are chemosynthetic (oxidize inorganic compounds to obtain their<\/p>\n
energy to produce their own food).<\/p>\n
\u00b7 These organisms are known as Photoautotrophs and Chemoautotrophs in that they manufacture their own food.<\/p>\n
Heterotrophic Nutition.<\/p>\n
They must obtain their energy and nutrients from other sources.<\/p>\n
For example:<\/p>\n
\u00b7 Saprophytic bacteria : digest materials in their environment by releasing powerful digestive enzymes. They then absorb the digested nutrients.<\/p>\n
\u00b7 Parasitic bacteria : rely on other organisms to provide the digested nutrients directly.<\/p>\n
Part Two: Interactions<\/p>\n
Bacteria can exist everywhere there is life this includes:<\/p>\n
in the air<\/p>\n
in the water<\/p>\n
in the earth<\/p>\n
on plants<\/p>\n
in organism<\/p>\n
\u00b7 without bacteria, we as humans could not exist<\/p>\n
\u00b7 bacteria are the most primitive form of life because they:<\/p>\n
a) grow and reproduce ( as often as one time every 15 minutes)<\/p>\n
b) they use nutrients to survive<\/p>\n
c) they have simple cell structures<\/p>\n
\u00b7 it is possible to see bacteria through a light or electron microscope<\/p>\n
Bacteria are both helpful and harmful
\nTo preserve or stop bacteria metabolism they can be:
\nchilled<\/p>\n
dried out<\/p>\n
frozen<\/p>\n
heated<\/p>\n
Dangerous bacteria are called pathogens because they cause diseases.<\/p>\n
to control pathogenic bacteria you can remove bacteria by:
\nremoving all bacteria using extreme heat<\/p>\n
wash with antiseptic soaps<\/p>\n
use antibiotics<\/p>\n
specific immunization for specific bacteria proteins<\/p>\n
Some bacteria can become resistant to antibodies by altering protein coat or structure of cell wall.
\nBacteria can change into dormant forms called spores, which allow the bacteria to stop metabolism in extremely harsh environments<\/p>\n
Useful Bacteria<\/p>\n
Most bacteria are not pathogenic — include decomposers, nitrogen<\/p>\n
fixing bacteria, vitamin producing bacteria, bacteria used to make<\/p>\n
insulin and growth hormone, bacteria used in dry cleaning, tanning,<\/p>\n
cheese, yogurt<\/p>\n
Essential Bacteria:<\/p>\n
Bacteria can be helpful because:<\/p>\n
\u00b7 they help plants absorb nutrients from the soil ( specifically nitrogen)<\/p>\n
\u00b7 they are used to make milk products such as yogurt, cheese and butter<\/p>\n
\u00b7 they can be used to manufacture antibiotics<\/p>\n
\u00b7 they can alter biproducts from sewage treatments into non toxic waste<\/p>\n
\u00b7 they can be used to produce specific gases such as methane<\/p>\n
\u00b7 they are used for fermentation<\/p>\n
Escherichia coli Gram – rod shape (bacilli)<\/p>\n
Sarcina lutea Gram + round shape (cocci)<\/p>\n
Bacillus subtilis Gram + rod shape (bacilli)<\/p>\n
Bacillus cereus Gram + rod shape (bacilli)<\/p>\n
Serratia marcescens Gram – rod shape (bacilli)<\/p>\n
Rhodospirillum rubrum Gram – spiral shape (spirilla)<\/p>\n
Harmful Bacteria<\/p>\n
Harmful bacteria can cause disease (Pathogenic) by interfering with the host’s normal routine, by destroying cells and tissues, by producing endotoxins and exotoxins, and by eliciting an immune response.<\/p>\n
\u00b7 An endotoxin is a toxin within the bacterium that is only released when the bacterium dies and it breaks down.<\/p>\n
\u00b7 An exotoxin is a toxin released by living bacteria.<\/p>\n
Koch’s Postulates: –<\/p>\n
used to prove that an organism is responsible for a particular disease.<\/p>\n
1. must be shown that the organism in question is always present in<\/p>\n
the diseased hosts.<\/p>\n
2. microbe must be isolated from the host and grown in a pure<\/p>\n
culture.<\/p>\n
3. microbe from pure culture must be capable of producing the<\/p>\n
disease symptoms in a new healthy host.<\/p>\n
4. microbes isolated from the newly infected host must be grown in a<\/p>\n
pure culture and compared to the original micro-organism.<\/p>\n
Examples:<\/p>\n
a) Respiratory Tract: Strep throat, Rheumatic fever, Scarlet fever;<\/p>\n
Pneumonia, Whooping cough, Diphtheria, Tuberculosis…<\/p>\n
b) Skin: Staph (pimples and boils), Leprosy, Gas gangrene…<\/p>\n
c) Nervous System: Tetanus, Botulism, Meningitis…<\/p>\n
d) Digestive System: Typhoid fever, Cholera, Dysentery; (food<\/p>\n
poisoning) Salmonella, Botulism, Staph…<\/p>\n
e) Venereal Diseases: Gonorrhea, Syphilis…<\/p>\n
Infection by bacteria<\/p>\n
There are three lines of defence through which bacteria must<\/p>\n
penetrate:<\/p>\n
a) through the strong epidermal tissue (skin).. .in wounds, pores,<\/p>\n
openings.<\/p>\n
b) phagocytic white blood cells which engulf foreign materials including bacteria.<\/p>\n
c) antibodies produced by other white blood cells.<\/p>\n
Active Immunity –<\/p>\n
– is slow acting (because the body is taking time to produce antibodies against the infection); but long lasting (because the body produces “memory cells” which “remember” how to produce these specific antibodies again).<\/p>\n
Normally produced by actual initial infection (chicken pox), or by using a vaccine (polio, smallpox). The vaccine consists of either weakened (attenuated) bacteria, dead bacteria, or artificial products which resemble the actual foreign invader (antigen).<\/p>\n
Passive Immunity<\/p>\n
This is fast acting (because the person is injected with antiserum containing the necessary antibodies or antitoxin); but short-lived (because the person does not actually produce the antibodies – hence no memory cells for the future!). The protein antibodies are often provided from the blood of a larger animal such<\/p>\n
as a horse! (Tetanus, Rabies). New techniques have been designed so that bacteria can produce specific antibodies. Newborns initially have Passive Immunity through the passage of antibodies across the placenta, and in the Mother’s milk. In some cases, injection of Toxoids stimulate the production of natural antitoxins.<\/p>\n
Antibiotics a biological substance which will kill or slow (inhibit) the growth<\/p>\n
of an organism.<\/p>\n
e.g. Penicillin, Tetracycline, Bacitracin, Ampicillin,<\/p>\n
Erythromycin…<\/p>\n
a) must be bacteria-specific.<\/p>\n
b) some people are allergic to certain antibiotics.<\/p>\n
c) some could kill off useful bacteria.<\/p>\n
d) may reduce the competitive pressure and allow<\/p>\n
harmful bacteria to survive.<\/p>\n
e) may cause resistant strains to develop.<\/p>\n
Other biocides include: Sulfur Drugs, antitoxins, various<\/p>\n
bacteriocides, disinfectants…<\/p>\n
Part Three: Changes with time<\/p>\n
Reproduction<\/p>\n
1. Bacteria reproduce mostly asexually by a process called BinaryFission. In this method, the circular ring of DNA replicates, and then the cell divides into two daughter cells — each with its own DNA.<\/p>\n
2. Some bacteria can also undergo sexual reproduction by a process called Conjugation. In this method, the “male” is connected to the “female” by a tube called a Pilus. The DNA from the “male” then travels through the tube to the “female”. Here, it recombines with the “female” DNA and the “female” bacterium then divides.<\/p>\n
Some bacteria can be Transformed into a different cell by absorbing fragments of DNA of other cells. In another method of producing recombined bacterial DNA, bacteriophages (viruses) carry portions of the bacterial DNA from one cell to another. This process is called Transduction.
\n4. When environmental conditions are not favourable, some bacteria are capable of forming highly resistant thick-walled Endospores until conditions once again return to normal.<\/p>\n
Part Four Form and Function<\/p>\n
Cell Structure:<\/p>\n
A bacteria cell has the following structures:<\/p>\n
Nuclear material in the form of DNA to pass on genetic information<\/p>\n
Cell membrane: which controls the flow of material in and out of a cell<\/p>\n
Ribosome: which assist in making cell proteins<\/p>\n
Cell wall<\/p>\n
Flagella<\/p>\n
Endospores<\/p>\n
Response to Stimulus:<\/p>\n
Bacteria Lab Questions:<\/p>\n
1. Why must you always use sterile technique when working with<\/p>\n
bacteria?<\/p>\n
2. What does “pathogenic” mean?<\/p>\n
3. What is an “inoculum”?<\/p>\n
4. List three general rules for handling bacteria.<\/p>\n
5. When is the Pour Plate Method of culturing bacteria used?<\/p>\n
6. Why must you be careful in regulating the temperature of the melted agar in the Pour Plate Method?<\/p>\n
7. In procedure 7 in each of the labs, why did you have to flame the mouths of the test tubes?<\/p>\n
8. What is the reason for using the streak plate method?<\/p>\n
9. What is the reason for using the Pour plate method?<\/p>\n","protected":false},"excerpt":{"rendered":"
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