Thrid Lecture: 6/5/2015

Topic: Bacteria ( part 2 )

Bacteria

Notes:
1) Anoxygenic bacteria undergo photosynthesis in anaerobic condition. They have gram negative cell wall and oxygen is not the product of photosynthesis. They have bacteriochlorophyll and they are non pathogenic.

2) Oxygenic bacteria undergo photosynthesis in aerobic condition. They have gram negatice cell wall and oxygen is released during photosynthesis. Water as electron donor and they have chlorophyll. They are non pathogenic and also called cyanobacteria.

3) To differentiate Chromatium sp. , Chlorobium sp. and Rhodospirillum sp. , we need to refer to their colour of granules and pigments. Chromatium contain purple sulfur, Chlorobium contain green sulfur while Rhodospirillum contain purple nonsulfur. Some of the cyanobacteria have trichome and heterocysts.

4) There are 6 groups of gram positive bacteria with cell walls:
a) Gram positive cocci
-Streptococcus sp. and Staphylococcus sp.
- Use metabolic test to differentiate Streptococcus and Staphylococcus.
- Streptococci are catalase postitive (form bubbles) and Staphylococcus are catalase negative.(do not form bubbles)

b) Endospore-forming Gram positive rods and cocci
- Bacillus ( aerobes or facultative anaerobes ) and Clostridium ( obligate anaerobes )
- Example: Bacillus anthracis. Clostridium botulinum, Clostridium tetani, Clostridium perfringens

c) Regular non-spore forming gram positive rods
- rod shape
- Example: Lactobacillus (friendly bacteria)
- Homofermentative is the characteristics of Lactobacillus where they only produce lactic acid through Embden-Meyerhoff pathway.
- Heterofermentative is the chatacteristics pf Lactobacillus where they produce lactic acid, ethanol and carbon dioxide through Pentose Phosphate pathway.

d) Irregular nonsporing gram positive rods
- club-shaped rod with side by side alignment of cells
- Snapping binary fission
- Example: Corynebacterium diphtheriae

e) Mycobacteria
-use acid-fast stain
-slightly curved to straight rods
-Slow grower
- time  needed to form cell wall contaning mycolic acid
- growth stimulated by lipid and fatty acids
- Glycerol-whole egg medium
-Example: Mycobacterium tuberculosis

f) Actinomycetes
- form mycelium but prokaryotes
- soil inhabitant
-produce antibiotic. For example: chloramphenicol, erythromycin, tetracycline
different actinomycetes have different composition and structure of cell wall, morphology and colour of mycelia and sporangia.
- they can recycle nutrient, degrade cellulose, lignin, chitin, latex, aromatic chemicals and keratin.
- Aerial filaments bearing reproductive spores which is known as conidia. Accumulation of conidia form the fluffy morphology.

5) Bacteria lacking cell wall are bacteria without regular cell wall or without cell wall. They are known as pleomorphic. the example of this bacteria is mycoplasma. They have strong plasms membrane which made up of sterols and lipoglycan. They form colonies with fried-egg appearance and require growth factors such as vitamin, amino acids and nucleotides.

Activities: The presentation from group Archae and the working of SCL from each group.

My Own Explorace:
1) Catalase is an enzyme used by bacteria to induce the reaction of reduction of hydrogen peroxide into water and oxygen.
2) Trichome is a chain of vegetative cells in cyanobacteria.
3) Heterocysts are specialized, pale-yellow,thick-walled cells with disputed function nitrogen-fixing formed during nitrogen starvation by some filamentous cyanobacteria.
4) The pictures of trichome and heterocysts:

5) Corynebacterium diphtheriae is the pathogenic bacterium that causes diphtheria. Diphtheria often come on fairly gradually beginning with a sore throat and fever. This can block the airway and create a barking cough as in croup. The neck may swell in part due to large lymph nodes. A form of diphtheria that involves the skin, eyes, or genitals also exists.

6) Serpertine arrangement of Mycobacterium tuberculosis:

7) Glycerol whole-egg medium provide fatty acids and protein neccessary for the metabolism of mycobacteria. The coagulation of the egg albumin during sterilization gives a solid medium for inoculation purposes

8) Vibrio cholerae can produce endospores but endospore will germinate after few hours the endospore formed. Therefore, Vibrio cholerae is not dorminant endospore forming bacteria.

9) Three in 10 Americans carry staph bacteria in their noses, where the germs live benignly unless they are allowed to enter the body through an open wound like a surgical incision. If one of these patients touches his or her nose and then the surgical site, the patient will get infected with Staphylococcus aureus infection. Doctors swab patients’ noses before surgery to test for Staphylococcus aureus bacteria. If the patient has Staphylococcus aureus bacteria naturally living in his or her nose, apply an antibiotic nose ointment in the days before surgery. Up to 85 percent of staph infections are caused by a patient’s own bacteria, meaning that we’re actually infecting ourselves.

10) Escherichia coli possess the ability to transfer DNA via bacterial conjugation, transduction or transformation, which allows genetic material to spread horizontally through an existing population. This process led to the spread of toxin from E. coli O157:H7 to other E.coli .

11) There are five basic mechanisms of antibiotic action against bacterial cells:

- Inhibition of Cell Wall Synthesis (most common mechanism)
- Inhibition of Protein Synthesis (Translation) (second largest class)
- Alteration of Cell Membranes
- Inhibition of Nucleic Acid Synthesis
- Antimetabolite Activity

12) Cutaneous anthrax is the most common form of anthrax infection, and it is also considered to be the least dangerous. When anthrax spores get into the skin, usually through a cut or scrape, a person can develop cutaneous anthrax. 

Reflection:

This is my first time to hear that antibiotic can be apply on skin and nostrils to kill the bacteria. I guess the endospore of Vibrio cholerae will germinate rapidly is because the survival condition of Vibrio cholerae is close and same with our normal condition. Therefore, when Vibrio cholerae reach its favoured environmental condition, it will straight away germinate. I learnt the use of the number in a journal. The number in the journal refer to the number of reference below the journal. This is to let the reader to check the content inside the journal from the reference given.