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, O 2  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 dies Ex.: 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! Disinfectants: UV light, bleach, lysol, etc. Used to disinfect objects Skin irritant & highly toxic if ingested, inhaled Antiseptics: hydrogen peroxide, alcohol, iodine, etc. Used topically (on skin) Toxic if ingested, inhaled Antibiotics: Drugs such as penicillin, erythromycin, etc. Used internally, taken orally or by injection Low toxicity, usually have side 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 food ex.: archaebacteria in hot springs / ocean vents  Saprophytic (decomposers)

Bacteria - Respiration  Aerobes – use oxygen ex.: tuberculosis bacteria  Anaerobes – do not use oxygen, perform fermentation ex.: 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

Binary Fission vs. Mitosis (prokaryote) (eukaryote) Reproduction & Recombination (increase number of bacteria) (DNA from different organisms combined) Sexual or asexual?

Endospore Formation Anthrax

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? 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 culture ex.: 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…