bacteria - identification microbiologists identify bacterial species by: cell shape - sphere, rod,...
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Bacteria - Identification
Microbiologists identify bacterial species by: Cell shape - sphere, rod, spiral Clumping styles - filaments, bunches Colony appearance – shape & texture Staining w/ dyes – based on cell wall composition Nutrition & respiration – food, O2
Surface/cell membrane molecules, such as proteins
** Sterile technique must be used to inoculate (introduce) bacteria into sterile
culture medium(agar or fluid) **
Sphere-Shaped Bacteria
One coccus, two cocci…
In chains - streptococcus
In twos –diplococcus
In bunches, staphylococcus
Rod-Shaped Bacteria
One bacillus, two bacilli…
Spiral-Shaped Bacteria
One spirillum, two spirilla…
Gram Stain
Uses two dies (blue and red) and two rinses: some bacteria retain both dies blue/purple
appearance = Gram-positive bacteria
Staphlococcus aureus Bacillus anthracis (anthrax) in cerebrospinal fluid
Gram Stain
Some bacteria retain only the red stain red/pink appearance = Gram-negative bacteria
Escherichia coli (E. coli)stained using the Gram method
Some strains of this bacterium cause food poisoning; others are harmless and help make vitamin K in our intestines.
Gram Stain
Some bacteria do not stain well with this method must use other diesEx.: tuberculosis bacteria
What can we infer about the physical and chemical characteristics of Gram-positive and Gram-negative bacteria? they must differ!
Lipopolysaccharide
Differences in Cell Wall Structure – Gram + vs. Gram - Bacteria
What kingdom and domain do these bacteria belong to?Prokarya/Bacteria, Eubacteria/Bacteria
Bacterial Colony Appearance
Inhibition Rings
Clear / clearer area where cell growth was inhibited
Anti-bacterial Substances
Higiene: Most germs are killed or removed with water & soap. Resistance: Germs may evolve resistance to drugs
Finish your antibiotic prescription as directed!
DisinfectantsDisinfectants::
UV light, bleach, lysol, UV light, bleach, lysol, etc.etc.
Used to disinfect objectsUsed to disinfect objects Skin irritant & highly toxic Skin irritant & highly toxic if ingested, inhaledif ingested, inhaled
AntisepticsAntiseptics::
hydrogen peroxide, hydrogen peroxide, alcohol, iodine, etc.alcohol, iodine, etc.
Used topically (on skin)Used topically (on skin) Toxic if ingested, inhaledToxic if ingested, inhaled
AntibioticsAntibiotics::
Drugs such as penicillin, Drugs such as penicillin, erythromycin, etc.erythromycin, etc.
Used internally, taken Used internally, taken orally or by injectionorally or by injection
Low toxicity, usually have Low toxicity, usually have side effectsside effects
How Antibiotics Work--Mechanisms of Action of Some Antibiotics
Penicillins: Inhibits formation of the bacterial cell wall by blocking cross-linking of the cell wall structure. The cell wall is a needed protective casing for the bacterial cell. Bacitracin: Inhibits cell wall production by blocking the step in the process (recycling of the membrane lipid carrier) which is needed to add on new cell wall subunits.Cephalosporins: Similar to penicillins in their mode of action but they treat a broader range of bacterial infections. They have structural similarities to penicillins and many people with allergies to penicillins also have allergic reactions to cephalosporins.
Aminoglycosides: Inhibit protein synthesis by binding to a portion of the bacterial ribosome. Most of them are bacteriocidal (i.e., cause bacterial cell death).
Rifampin: Inhibits RNA synthesis by inhibiting one of the enzymes (DNA-dependent RNA polymerase) needed in this process. RNA is needed to make proteins.
Quinolones: Blocks DNA synthesis by inhibiting one of the enzymes (DNA gyrase) needed in this process.
Bacteria - Nutrition
Most are heterotrophs Some autotrophs
Photoautotrophs Photosynthetic, most have chlorophill
ex.: cyanobacteria Chemoautotrophs
Use ammonia or sulfur to make own foodex.: archaebacteria in hot springs / ocean vents
Saprophytic (decomposers)
Bacteria - Respiration
Aerobes – use oxygenex.: tuberculosis bacteria
Anaerobes – do not use oxygen, perform fermentationex.: tetanus bacteria
Obligate aerobe/anaerobe can only survive under the condition; ex.: obligate aerobes need oxygen
Facultative aerobes/anaerobe can live with or without the condition; ex.: facultative anaerobes grow better in anaerobic conditions, but can tolerate oxygen
Bacteria - Reproduction
Reproduce mostly asexually by binary fission
May reproduce sexually by conjugation Some form dehydrated spores, or
endospores survive hard conditions, start growing again when water/food available
http://www.cellsalive.com/ecoli.htm
Binary Fission vs. Mitosis
(prokaryote) (eukaryote)
Reproduction & Recombination(increase number of bacteria) (DNA from different
organisms combined)
Sexual or asexual?
Endospore FormationAnthrax
Recombination
Genetic Changes by three means:
1. Conjugation – exchange plasmids
2. Transformation – absorb DNA from environment
3. Transduction – DNA via viruses
1. Conjugation
Which Bac-t is the F+?
Which Bac-t is the F-?
Which Bac-t is donating the plasmid?
Which Bac-t is receiving the plasmid?
1
2
2
1
1
2
Is this an example of Bacterial Reproduction or Bacterial Recombination or Both?
Sex pilus
Transformation
Biotechnology techniques can be used to “transform” bacteria so that they will express a gene from another organism:
Copies of the desired gene are synthesized and added to the bacterial cultureex.: gene for insulin protein
Bacteria are exposed to an electrical current or other type of “stress” – this causes them to take in the pieces of DNA around them
The transformed bacteria are grown in culture and the new expressed protein can be isolated
Purified protein is used in research, medical treatment, etc.
2. Transformation
Smooth Strain(Virulent, causes Pneumonia)
Rough Strain(Harmless)
Capsules
l
Transformation of Bacteria
OUCH!
3. Transduction – virus takes some of Bacterial DNA
Step 1
Step 2
Step 3
Step 1
Step 2
3.Transduction – viral DNA inserted into bacterial DNA
How do bacteria cause disease? Exotoxins – secreted by living bacteria
Endotoxins – released when bacteria die
Stealing resources / nutrients from host
Interfering with proper functioning of body cells
Bacterial Disease Examples
Dental caries Food poisoning –
Salmonella, E. coli “Staph” – S. aureus “Strep” – S. pyogenes Tuberculosis Lyme disease Black plague Cholera
STDs – gonorrhea, siphilis, chlamydia
Gangrene – causes tissues to die, loss of limbs
Septicemia – blood infection
Anthrax Meningitis Tetanus The list goes on and
on and on…