Microbe growth

Question 1

An algae that does not require microscopy to be seen. It is the largest single celled organism.

Answer 1

Caulerpa taxifolia

Question 2

Inventor of the single lens microscope, allowing for the first observations of microbes and living cells.

Answer 2

Anton van Leeuwenhoek

Question 3

Discovered flies do not spontaneously generate

Answer 3

Francesco Redi (1688)

Question 4

Swan neck, broth boiling experiment

Answer 4

Louis Pasteur (1861). Discovered that microbes do not spontaneously generate.

Question 5

Macronutrients

Answer 5

Needed in large amounts. Carbon, Nitrogen, Phosphorous, Hydrogen, Oxygen, Sulfur, are used as components of Nucleotides, carbohydratesm lipids and proteins. Macronutrients such as Magnesium, Iron, Potassium, and Calcium are used as Enzyme-cofactors and regulatory molecules.

Question 6

anapleurotic reactions

Answer 6

Interconversion between different small molecules. This can be facilitated via the TCA cycle/Reverse TCA cycle, gluconeogenesis.

Question 7

Amino Acids

Answer 7

They can be used to make proteins. They require transporters, specific enzymes are needed to allow the cell to scavenge AAs from their environment. They can enter the TCA cycle to yield ATP and reducing power. Though the transporters use ATP or Proton motive force to import AAs and the cell may use PMF to power the flagella to swim to AAs.

Question 8

Glucose

Answer 8

Sugars are important parts of the cell wall. They can be converted into ribose sugar for forming nucleotides. They can be broken down during glycolysis and the TCA cycle, yielding ATP and reducing power. The transport and glycolysis of glucose requires input of high energy phosphate to start, therefore when energy is entirely depleted the bacteria can not metabolise new glucose.

Question 9

Oxygen

Answer 9

It is a key component of many biomolecules. Oxidative damage can impose high biosynthetic cost to repair. It is the terminal electron acceptor for the electron transport chain.

Question 10

Caulobacter crescentus cell cycle

Answer 10

It uses check points and no-overlapping events. The swarmer Caulobacter cell (G1) binds to a surface, becoming a stalked cell (S). The stalked cell then divides, forming a free swarmer cell (S, G2, M). There are many proteins involved in regulating the Caulbacter crescentus cell cycle. DnaA is activated, initiating DNA replication and activating GcrA which repressed DnaA and promotes CtrA. CtrA represses replication initiation and represses GcrA and CtrA. It promotes DivK, FtsZ and CcrM. CcrM promotes DnaA and GcrA while repressing itself and CtrA. DivK and FtsZ help promote cell division.

Question 11

Multifork Progression

Answer 11

Mutlifork Progression explains how it can take 20 minutes for bacteria to reproduce, despite chromosome replication taking 40 mins and division taking 20. During fast growth, initiation of gene replication occurs before the previous round of replication is done.

Question 12

35 min Cell cycle

Answer 12

At T0, the newly divided cell inherits a partially replicated chromosome. At T10, before replication is over, 2 new replication events are initiated. At T15, replication is complete for the inherited chromosome, cell division begins. At T35, cell fission happens, with the cells separating.

Question 13

Origin initiation

Answer 13

The origin (oriC = 254 bp) is initiated and forms two bi-directional replication forks. DnaA binds to the DnaA box sites in the origin. It initiates origin melting, opening up the DNA for helicase loading. DnaA-ATP form has a high affinity to the binding sites. It is dependent on the metabolic state of the cell (more ATP, more DnaA-ATP, more replication). The ratio of DnaA-ATP to DnaA-ADP peaks during initiation

Question 14

Inactivation of the origin

Answer 14

The origin needs to be shut off to replicate again. The origin can not be fired too often as that would waste nutrients. SeqA binds to the newly replicated origin, condensing the strands to prevent access of other binding proteins. SeqA prefers newly replicated hemi-methylated sites. SeqA targets the GATC sites of the origin region, behind the advancing replication fork. Dam methylase binds to the GATC binding sites after SeqA, methylating the newly synthesized strand, this decreases SeqA binding. DnaA-ATP decreases after origin firing, with Hda proteins helping in increasing hydrolysis.

Question 15

Bacterial Nucleoid

Answer 15

This is the region of the bacteria that contains the genetic material. The nucleoid has many associated proteins. Fis = regulator of virulence associated genes. HNS = Manages genome evolution, condensation and transcription. MukB = Dna binding and reshaping, chromosomal organiser. IHF = phage encoded transcription regulator. DPS = Protects the nucleoid from damage. Hu = histone-like protein

Question 16

MukBEF

Answer 16

E. Coli structural maintenance of chromosomes (SMC) complexes. MukB forms a V shaped dimer with C and N terminal domains, forming a globular ATP-binding head. ATP-hydrolysis generates movements. MukB helps localise oriC. ParC and ParE help in MukB localisation

Question 17

Involved in cell wall synthesis, Transporting dissacharide pentapeptides into the periplasm to be incorporated into the peptidoglycan layer

Answer 17

Mray, MurG, and FtsW-RodA.

Question 18

Transpeptidase

Answer 18

Cross links and incorporates peptidoglycan

Question 19

Transglycosylase

Answer 19

Extend the sugars of dissacharide pentapeptides to form long peptidoglycan in the periplasm.

Question 20

Antibiotic that prevents elongation.

Answer 20

Mecillinaun. Its blocking of elongation causes the bacteria to form a spherical shape.

Question 21

Antibiotic that prevents Cell division.

Answer 21

Furazlocillin. Blocks cell division, causing a long filament to from.

Question 22

Elongasome

Answer 22

Cytoplasmic cytoskeleton that recruits and localises transmembrane peptidoglycan synthases. It’s an actin-like discontinuous helix that guides the cell wall synthesising complex. In E. coli, MreB is the main protein the Elongasome is composed of.

Question 23

Eligongasome

Answer 23

MreB is an actin-like protein which can undergo ATP-binding and hydrolysis. MreB binds to the lipid bilayer when ATP is present. MreB assembles as pairs of protofilaments that connect cell wall synthesising complexes during elongation.