topic 4 bcterial genome cloning & AMR

What is a genome

All the dna within a cell ( chronometer plasmids and other genetic elements )

Describe the structure of the bacterial chromosome

• usually one circular chromosome

• Condensed into a nucleoid

• The size of the structure is linked to its complexity and function capability

What is the structure of the bacterial nucleoid

No membrane boundary - so bacteria diffuse in slow growing cells

In growing cells typically in the centre and bi lobed

Chromosome organised into large supercooled domain loops

The dna has a variety of proteins bound to it ( histones like anchoring proteins )

How does binary fission occur

Single cell dives into two identical daughter celll

Bacteria increase in length and mass

Nucleoid expanded ( semi conc rep )

Synthesis pd a septum in the model ( cause cell to split into two )

Explain the ways plasmids replicate

Autonomous replication - independent of chromosome j

Describe what the oric and terc sites are

Oric - origin of replication site

Terc - is termination point

Replication of bacterial chromosomes is bidirectional forms two replication forks ( which both replicate dna in there respective directions )

So two replisomes approach each other at the terc site

Describe how chromosome replication and cell division are tightly controlled

Chromosomes attach to the oric a the equation fo nuclear envelope

2 replication forks fork

The two oric sites move apart as cell expands

Terc site stays in the middle

The completion of replication triggers Ftsz which forms a ring complex

That tells the cells that dna chromosome are separated the cell can divide

Expalin the balance bacterial cells must do to make sure cells replicate and divide effectively

Chromosome replication time is independent to grwoth rate

Time to replicate chromosomes - 40 min

But cell division can happen every 20 in

DNA replication is longer then cell division

Therefore to create a balance the next round of dna replication is dinnitated before the first one is complete that way cells are ready to divide at the same time

So instead of having two replication forks yu have four 2 for one set of division and 2 for the next set of division

What are the functions of plasmids

In most bacteria

Genes encoding proteins and rna

Not essential for host growth

Used for adaptation selective advanatages in specific conditions

How does plasmid replication occur

Autonomous replication independent of chromosomes

They have a fixed oric site

Many control systems Use functional rna’s

Use host dna for function use hosts dna polymerases

Short replication tiem ( 6 seconds)

Self regulating

Plasmids have a fixed copy ( they regulate there own number of copies)

Copy control - they cant have the sae copy control in the same cell it leads to incompatibility ( tow plasmids that have the same function)

What are the roles of plasmids

Conjunctive plasmids - transistor blue sequance transfer

Tumour induction

Resistance plasmids - resist antibiotics metals anti microbial production

Recombinant dna technology

What are bacteriophages

They eat bacteria

Protein coy containin phage genome

Very small

Presence detected by plaques

Cell lysis

Insertion into chromosomes

Not enter lytic cycle

What are the three mechanisms of genetic exchange in bacteria

Conjugation - transfer of dna direction between bacterial cells ( cel to cell contact ) ( plasmids )

Transformation - bacteria take up dna from there environment ( natural transformation cells must become competent to take up DNA

Transduction - transfer of dna between bacterial cells via bacteriophages ( phases infect cell replicate and produce new phage viruses )

What is dna cloning

He process of making multiple identical copies of a particular piece of dna

What is a genome library

Collection of dna fragments that have been cloned into vectors

Genomic libraries are collection of consists of overlapping dna fragments that together make up the total genomic dna of an organism

What is a cDNA library

Collection of dloned dna sequances that are complementary to the total mRNA extracted from an organisms respective of all the genes that are expressed

What are the essential features to clone genes

Maintenance replication in host cell

Resctriion enzyme site - insertion of foreign dna fragment

Metho to introduce into host cell

Genetic selection markers

Identify recombinant

How do you construct a genome library

Isolate chromosomal dna

Digest with restriction enzyme

Ligase chromosomal dna with vector dna

What is anti microbial resistance

When bacteria viruses fungi and parasites change over them to no longer respond to medicine

Making them harder to treat

What are anti microbials

An resistance

Compounds that stop or slow the stead of microorganisms

Including antibiotics antifungal anti parasitic and antiviral drugs

Resistance - microorganisms are no longer controlled or killed by an anti microbial

What ate some ways antibiotics work

In I hit cell wall synthesis - prevents peptidoglycon cross linking

Inhibits dna synthesis - inhibits dna gyrase

Inhibits protein synthesis blocks ribosomes prevent it carrying out natural functions

Disrupts bacterial cells wall - punctures holes in bacteria preventing the maintainnce of osmotic pressure

The theory of selection

Organisms with advanagaous traits are more likely to survive changes in the environment eg - antibiotics