Lecture 2- Bacterial Food Borne Illness

Question 1

Cell wall protects the cell from bursting due to turgor pressure. What is turgor pressure?

Answer 1

exists because bacteria live in environments that are more dilute than the cytoplasm. This causes a net influx of water. This results in pressure (turgor) being directed out against the cell wall

Question 2

What color would a gram positive cell be after a gram stain?

Answer 2

Retain the dye and remain violet because the peptidoglycan membrane is thick and the first layer.

Question 3

What color would a gram negative be after a gram stain?

Answer 3

Pink and would not retain the dye because the peptidoglycan membrane is trapped between the outer lipid membrane and plasma membrane

Question 4

Surface structures of Gram positive (4)

Answer 4

1. Teichoic acids: can compromise 30-60% of the dry cell weight, anchored to peptidoglycan, several functions
2. Capsule: used in classification, varies of roles. It is a polysaccharide layer that lies outside the cell envelope of bacteria
3. Fimbrae and Pili: PRO on the cell surface found in some gram positive
4. Flagella: organelle of locomotion

Question 5

Surface structures of gram negative (4)

Answer 5

1. Lipopolysaccharide: consists of lipid A, core, and repeating oligosaccharide (O-antigen)
2. Capsule: used in classification, variety of roles. It is a polysaccharides layer that lies outside the cell envelope of bacteria
3. Fimbrae and Pili: PRO on the cell surface found in most gram negative
4. Flagella: organelle of locomotion

Question 6

Fimbrae and Pili

Answer 6

PRO fibrils extending from the cell surface found in most gram negative and a few gram positives

• Function: mostly unknown, many mediate attachment to tother cells
• Adhesive pili have adhesions which are PRO in the pili that allow the pili to stick to things
• Some mediate genetic exchange

Question 7

Sex Pili

Answer 7

• used for bacteria to attach to each other and transmit DNA from a donor cell to a recipient cell
• found in enteric bacteria (e.coli, pseudomonas) but are not universal among bacteria

Question 8

Serotyping based on the cell surface structures of bacteria which includes: (4)

Answer 8

1. Capsule K antigen: Capsular Polysaccharide associated with cell surface non-covalently and protects bacteria from host immune system. The K antigen repeats units from a high molecular weight structure called as capsule
2. Lipopolysaccharide O antigen: aka lipoglycans and endotoxins, are large molecules consisting of a lipid and a polysaccharide composed of O antigen, outer core and inner core joined by a covalent bond; they are found in the outer membrane of gram-negative bacteria, and elicit strong immune responses in animals
3. Fimbriae F antigen: PRO antigen found on the surface of some gram-positive, and some gram-negative bacteria, rarely used in classification
4. Flagella H antigen: based on reaction with the flagellin PRO, that arranges itself in a hollow cylinder to form the filament in a bacterial flagellum

Question 9

Which bacteria has two chromosome instead of one?

Answer 9

Vibrios

Question 10

What does it mean when we say that bacterial chromosomes are plastic?

Answer 10

the combinations of genes present will be different in every isolate, some will be missing genes, and others will have genes which are unique to them

Question 11

Core genome

Answer 11

genes that are shared by all members of a certain groups

Question 12

pangenome

Answer 12

genes that are present in any member of a certain group

Question 13

accessory genome

Answer 13

genes that are present in a subset of members of a certain group

Question 14

Lytic pathway

Answer 14

• Viral DNA replicates
• Coat PRO synthesized, virus particles assembled
• Bacterial cell lyses, this releases new infectious virus particles

Question 15

Lysogenic Pathway

Answer 15

• Viral DNA is integrated into host DNA

- Cell divide and normal cell growth follows

Question 16

Lysogenic conversion

Answer 16

the process by which a prophage converts a nonpathogenic bacteria to a pathogen

Question 17

Defective Prophage:

Answer 17

A bacterioprophage that can no longer form infective phage due to the loss of essential genes

Question 18

Plasmids definition

Answer 18

• Circular molecules of double-stranded DNA which are self replicating
• they can be passed from different unrelated species of bacteria
• they don’t carry essential genes, they carry genes which encode for products which can benefit the bacteria under certain circumstances

Question 19

Transposons

Answer 19

• DNA elements that can hop from one place in chromosomal DNA to another
• Insertion Sequence (IS) Elements: smallest transposons, really only encode the transposon, can interrupt gene function by inserting in the middle of a gene, usually have an inverted repeat (IR) at either end
• Composite transposon: when 2 IS elements bracket other genes and carry those other genes with them when they move

Question 20

Intoxication

Answer 20

• occurs after the ingestion of a bacterial or mould toxin, d/t growth of the bacteria or mould in the food
• the toxin must be present in its active form
• once the toxin has been produced viability of the microorganism is no longer relevant
• Toxins are often better able to withstand processing better than the organism

Question 21

Infection

Answer 21

• illness occurs after the consumption of viable bacterial cells or viruses

Question 22

Toxicoinfections

Answer 22

• illness occurs from the ingestion of a large number of viable cells of some pathogenic bacteria through the consumption of contaminated food or water
• the bacterial cells wither sporulate, colonize, or die, and release the toxins