Bacterial Envelope and Bacterial reproduction

Question 1

bacterial cell wall is made of what?

Answer 1

peptidoglycan ! - series of disaccharide polymer chains with aa.

• its more elastic than cellulose
• it is also porous : so it allows large molecules to pass through
• many antibiotics attack the aa crosslinks of peptidoglycan.

Question 2

gram positive bacteria

Answer 2

thick peptidoglycan cell wall prevents the gram stain from leaking out. purple in colour.

Question 3

what is the space between the plasma mem and the cell wall called?

Answer 3

periplasmic space, it has proteins that help bacteria get nutrition

Question 4

gram negative bacteria

Answer 4

appear pink. they have thin peptidoglycan cell wall - so the stain is washed off. outside the cell wall, they have a phospholipid bilayer. - which is permeable - this bilayer has lipopolysaccharides which protrude outwards, - this can be a barrier to antibodies and many antibiotics.

Question 5

Many bacteria are wrapped in either ____ or ___ layer

Answer 5

capsule or a slime layer
both are made from polysaccharide .
slime layers are washed off , capsule can’t be.
capsule can prevent phagocytosis , desiccation, some viruses, and some components of the immune response.

Question 6

some gram negative bacteria have a fimbriae or pili

Answer 6

these attach a bacterium to solid surface . NOT INVOLVED IN MOTILITY.

Question 7

What are bacteria flagella?

Answer 7

long, hollow, made from globular protein flagellin.
do not confuse with eukaryote flagella with is made of microtubules.
bacteria flagella rotate counterclockwise and propel the bacterium in a single direction.
flagellum is propelled using energy from a proton gradient rather then ATP.

Question 8

Bacteria do not undergo mitosis or meiosis and they cannot reproduce sexually. They have 3 forms of genetic recombination

Answer 8

conjugation
transduction
transformation

Question 9

bacteria are also capable of undergoing a type of cell division called ?

Answer 9

binary fission! - asexual reproduction. - cell divides and two daughter cells are made which are genetically identical.

Question 10

what is conjugation?

Answer 10

needs one bacterium to have a plasmid with the gene that codes for the sex plus. Plasmids are small circles of DNA that exist and replicate independently of bacterial chromosome. plasmids are not essential to a bacteria that carry them and not all plasmids can initiate conjugation. you need a conjugate plasmid

Question 11

conjugate plasmids posses the gene for ?

Answer 11

sex pilus- which is a hollow protein tube , that allows two bacteria to connect so that DNA can pass thru the plus.
the plasmid replicates differently than the bacterial DNA

Question 12

What is the F plasmid?

Answer 12

called the fertility factor or the F factor!bacterium with the
F plasmid is called F +

Question 13

what is the R plasmid?

Answer 13

it denotes resistance to antibiotics. Its also a conjugative plasmid.

Question 14

what is transformation?

Answer 14

bacteria can incorporate DNA from their external env into their genome. env could be the lab or other dead bacteria. ex) heat killed bacteria mixed with live bacteria.

Question 15

what is transduction?

Answer 15

occurs via virus (vector). ex ) when a bacteriophage mistakenly encapsulates a DNA fragment of host bacteria and it then injects that bacterial DNA into another host. this can be mediated artificially in the lab

Question 16

some gram positive bacteria can make endospores which can lie dormant for 100s of years. what are endospores?

Answer 16

they are resistant to UV, chemical disinfectants and desiccation. endospore formation is usually triggered by lack of nutrients. the endospore must be activated before it can germinate and grow.