Exam 2: Microbial Growth

eukaryotic reproduction

sexual or asexual & haploid or diploid

haploid

unpaired chromosome/ one copy

diploid

paired chromosomes

number of human chromosomes

23 pairs, total 46

every single organism has ss __ and ds___

RNA, DNA

prokaryote reproduction

haploid only, asexual (binary fision, budding, filamentous)

Why do prokaryotes not use gametes to reproduce?

Because gametes are haploid to begin with, if two gametes come together the prokaryote would be considered diploid instead of haploid

filamentous reproduction

grow into hyphae

budding

mother cell gives rise to multiple daughter cells (yeast and some bacteria)

binary fission

one cell will grow to twice itself and split itself in half

What two aspects need to be considered when talking about binary fision?

Microbe & environment
(ex: vibrio cholerae, can replicate in 7 minutes if ingested)

OriC

gene/ DNA sequence for origin of replication

replisome

complex that binds to OriC with DNA Polymerase and other machinery for replication, begind to replicates in both directions until reaching ter (terminus)

ter

terminus gene, where replisome stops and results in two connected loops of chromosome

Why is it important for the loops of chromosome to be pulled apart in opposite directions?

it allows an equal split resulting in one chromosome in each

what protein is found in the middle of the cell?

FtsZ

will bacteria replicate/grow in unfavorable environment?

bacteria will not replicate and grow in unfavorable environment

Example of Chromosome partitioning

ParABS system in C.crescentus

parS

DNA sequence part of ParABS system

How many copies of parS are there when replication begins using the ParABS system?

2; as soon as replication starts another copy of parS is made because it is so close to oriC that begins replication in both directions

What is parS binded by?

ParB (binding protein)

what does crescentus attach to replicate?

a hard surface with a stalk

parB interactions

binds to parS and interacts with cell membrane to hold one chromosome close to the stalk

If parB holds one chromsome what holds the other one?

the other parS bound by another parB to pull to the other end of the cell using parA

ParA function in ParABS system

ParA polymerizes, binds to ParB and depolymerizes (pulls away) 2nd chromsome to other end (not stalk end)

What percentage of bacteria have the ParABS system?

70%

MinCDE system

protein spatial regulation mechanism that ensures accurate binary fission by preventing cell division from occurring at the cell poles

Can you have a Z ring where MinCDE is absent?

Yes, MinCDE accumulate to the left and right leaving middle bare where Z ring is supposed to form

If MinCDE fails can the cell find the center?

No, MinCDE dictates where center is located and FtsZ forms anywhere

MinCDE protein accumulation pattern

polymerizes to the left then depolymerizes and polymerizes on the right (is more like ping pong)

Found in the middle of the cell in addition to the Z ring

machinery necessary to make peptidoglycan

True or False: FtsZ is an integral protein

False

What does FtsZ need to do in order to have an effect on the cytoplasm for replication?

Interact with integral protein FtsA/ZipA (A =anchor)

Peptidoglycan synthesizing enzymes

bind NAM NAG via B1,4 glycosidic bonds, 5 amino acids, takes precursor from cytoplasm into periplasmic space to add

Cell wall size in replication

grows in order to accommodate for increased intracellular content during replication

Transpeptidases/ Penicillin binding proteins (PBPs)

enzymes that form bond between 3rd and 4th amino acid of NAM NAG units (transpeptidation)

why are Pencillin Binding Proteinss called PBPs?

That’s what penicillin targets DOES NOT COME FROM PENICILLIN

Autolysins

break covalent bonds (B 1,4 glycosidic) to break peptidoglycan apart in order to add more between

Relationship between penicillin and autolysins

penicillin inhibits transpeptidation while also activating autolysins leading to cell having no protection in hypotonic environment (water rushes in= cell lysis)

type of bond that peptide is

covalent bond

How do we bring NAM & NAG to periplasmic space?

1. NAM-pentapeptide binds to bactoprenol= Lipid I

2. NAG is added to Lipid I (NAM NAG unit created) = Lipid II

3. Flippase (in to out) takes bactoprenol NAM&NAG from cytoplasm to periplasmic space

4. In periplasmic space NAM & NAG are added to whole made by autolysin

Vancomycin function

inhibits cell wall synthesis by inhibits removal of 5th amino acid (terminal amino acid) (alanine)

Bacitracin function

inhibits bactoprenol from flipping

what anitbiotics inhibit cell wall synthesis

penicillin, bacitracin, vancomycin

growth

population growth rather than growth of individual cell

2 components of bacterial growth

increase in cell number and increase in cell size

growth curve chart descritpion

logarithm of cell number vs time

5 stages of growth curve

1. Lag

2. Log/exponential

3. Stationary

4. Death

5. Long term stationary

Lag phase

preparing to replicate, volume increases but number of cells stays the same

Exponential/ Log

growth rate is maximal

Stationary phase

no net gain no net loss, bacteria alive but not replicating (NO FtsZ present)

Death Phase

viable but not culturable (VBNC), programmed cell death can occur

Long term stationary phase

evolution occurs, increased waste leads to adaptation, mutation allows for growth on waste which creates new waste

lag phase may or may not occur

When will lag phase occur?

from stationary or death into fresh medium OR from exponential phase into a fresh medium of DIFFERENT chemical composition OR from rich to poor culture

biphasic growth

from rich to poor culture (ex: glucose → lactose)

In what medium will bacteria go through lag?

KIA (if bacteria can ferment lactose it can ferment glucose)

Is VBNC the same as sporilation?

NO, they are not dead they are just not able to be cultured in a petri dish (common for some pathogenic bacteria like V. cholerae)