Pharmacology 2060A/B Lecture Notes - Lecture 16: Gram Staining, Gram-Negative Bacteria, Genitourinary System
15 May 2018
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Module 16 – Antibiotics
16.1 – Bacteria
- Bacteria are single celled organisms that can be shaped as rods, spheres, or spirals
- Bacteria occupy almost every habitat on Earth, including humans!
o Have normal bacteria in our skin, mouth and intestinal tract
- Most bacteria are rendered harmless by our immune system and some even play beneficial
roles
- However, some bacteria are pathogenic and cause diseases such as cholera, syphilis and
tuberculosis
- Before the discovery of antibiotics, bacterial infection was a major cause of morbidity and death
Bacteria pathogenicity
- Virulene factors: things bacteria can use to cause infection
- Bacteria have a number of virulence factors that they use to cause infection
- Virulence factors include:
o Fimbriae and pilli
o Flagella
o Secretion of toxins and enzymes
o Invasion of host
1. Fimbrae and pilli
- Fimbriae and pilli are hair like structures that project from the surface of bacterial cells
- They allow bacteria to attach to certain sites in our body so they are not washed away
- For example, the bacteria E. coli are known to cause bladder infections
o E. coli produce fimbriae that attach to the urogenital tract
2. Flagella
- Bacteria typically live in aqueous environments and need to move to sites where they can
survive
- The flagellum that ateria possess allos the to si through the ater eiroet of
our body to the site where they may survive
- Ailit to si allos the ateria to oe to areas
where they can survive and colonize
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3. Toxins and enzymes
- Some bacteria secrete toxins and/or enzymes
- Secreted toxins can have a wide array of effects including nausea, vomiting, diarrhea, cramps,
pain, fever, or even paralysis
- Bateria do’t alas eed to e iside our od for the tois to produe a respose
- In some cases, bacterial toxins produced outside of our body can mediate toxic reactions if they
gain entry to our bod
o A good example is what occurs in some cases of poisoning
o Bacteria colonize food and secrete toxins
o When we ingest the food, we get symptoms of food poisoning
- In addition to toxins, bacteria also release enzymes
- Some enzymes can degrade tissue or breakdown antibodies, our defense against infection
4. Invasion
- Some bacteria can actually invade (enter) our cells
- E.g. the bacteria that cause Salmonella invade cells of the intestine and cause severe diarrhea
- Bateria that ause tuerulosis usuall eter our od i the lugs ad a hide iside ells
making it impossible for our immune system to act on them
Gram staining of bacteria
- Gram staining is a technique that is used to classify bacteria as either gram positive or gram
negative
- The gram stain tells us about the cell wall structure of bacteria, in particular the amount of
peptidoglycan in the cell wall
- This can be important in the determination of which antibiotic we use
- Gram positive cells have a thick peptidoglycan wall that stains purple during gram staining
- Gram negative cells have a thin peptidoglycan layer and stain pink during gram staining
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find more resources at oneclass.com
Gram positive vs. gram negative bacteria
- Both have flagella
- Gram positive: thick peptidoglycan (cell wall) layer
- Gram negative: thin peptidoglycan later
- Surface protein in gram positive bacteria is techoic acid and it is absent in gram negative
bacteria which have a different surface protein
- There are porin proteins that allow the entry of certain molecules into gram negative bacteria
and they are absent in gram positive bacteria
- Gram negative:
o Inner cell membrane
o Thin peptidoglycan cell wall layer
o Outer cell membrane
- Gram positive:
o Inner cell membrane
o Thick peptidoglycan cell wall layer
o No outer cell membrane (unlike gram negative)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Bacteria are single celled organisms that can be shaped as rods, spheres, or spirals. Bacteria occupy almost every habitat on earth, including humans: have normal bacteria in our skin, mouth and intestinal tract. Most bacteria are rendered harmless by our immune system and some even play beneficial roles. However, some bacteria are pathogenic and cause diseases such as cholera, syphilis and tuberculosis. Before the discovery of antibiotics, bacterial infection was a major cause of morbidity and death. Virulene factors: things bacteria can use to cause infection. Bacteria have a number of virulence factors that they use to cause infection. Virulence factors include: fimbriae and pilli, flagella, secretion of toxins and enzymes. Fimbriae and pilli are hair like structures that project from the surface of bacterial cells. They allow bacteria to attach to certain sites in our body so they are not washed away.
