Bacterial cell biology 2

In Gram negative have

• 2 membranes - inner and outer membrane

• between them have small peptilaglycon layer

In gram positive have

• 1 membrane and pepetilagoliocon layer is attached to membrane

Which bacteria do most antibacterial attack

• gram positive and only 1 membrane (more difficult with gram - as 2 membranes)

what can bacteria have on outside

• capsules (structred) - pollysacharde proetin layer on outside

• slime capsule (loose and deformed)

What is the function of these

• Virulence factors - protect them against host immune system

• Aid attachment to solid surfaces

• Biofilm formation

• Prevent dehydration/desiccation

Cell appendages

• Fibreae

• Pili

• Flagella

  (things that extend out of cell)

Function of Fimbrae

• short

• lots of them

• help its stick to surfaces

• no active function

Function of Pili

• longer than fibrae

• few per cell

• present in all gram - some gram +

• they allowing:

  • Function of secretion systems (bring things form inside to outside)

  • Cell movement - twitching motility

  • Important for genetic exchange (e.g horizontal gene transfer)

Secretion systems in Gram -

• Different types of secretion systems

• Molecules that bring things form inside of cell to other side of cell membrane

• Powered by ATP

• Type 4 secretion system well studied: transports enzymes, toxins, proteins and DNA

• Type 4 pilus extends form type 4 secreation system involved in ; conjunction, transformation and electron transduction

3 mechanism of horizontal gene transfer

• Conjugation

• Transformation

• Transduction

Conjugation

• How genetic info is transferred

• Plasmid with resistant gene replicate and passes through pilus secretion system to another cell

Trasfoemtaion

• Pick up DNA form environment

• Pilus extends to environment picking up DNA fragments from dead cells or secreted cells

• enter through pilus and gen encouperated in to genome

Transduction

• Happens through virus - Bacteriphage

• once infect cells with there DNA can either :

  • Cause cell to burst and release more viruses - LYSIS

  • Or can hide in genome for a while and then cause the cell to burst

type 4 secretion system can be used in different ways to attack other cells:

• secreate things to attack other cells

• inject things to harm cells

• move into cells and then produce toxins

what are PHBs and PHAs

• PHBs are polymers, different types called PHAs

• made in carbon rich environment

• get broken down when in environment lacks carbon or they need it

Phosphate

• bacteria store phosphate

• Phosphate used to make nucleic acids, bi-layer…

• stored as inoragnic PI to be used in times or need

Sulfur

• can be generated in bacteria through reduction of things like H2S in fermentation

• this releases electrons to be used in metabolism or CO2 fixation

• Sulfur element stored in periplasam of cells to protect them

Carbon materials

• some bacteria store carbonate material through Biominerlization

• Cyanobacteria provide ballast to keep it stay deep in water column - weighs it down

Magnetosomes:

• in bacteria can form tiny magnets

• build magnetic particles enclosed in membrane

• MF line is aligned with going deeper or shallower into the water

Gas vesicles

• Provide cyanobacteria the ability to float

How are gas vesciles formed

• formed form 2 proteins GvpA and GvpC

• GvpA is small hydrophobic proetin, rib like structures, keeps gas in and water out

• GvpC cross links GvpA , increases strength of vesicles

what are bacterial micro compartments (BMCs or MPSs)

• proetin enclosed structures that allow metabolic reactions to occur that would have been otherwise toxic to the cell

Examples of BMCs

• Carboxysomes → allow photosynthesis within them , stores RuBisCo and concentrated carbon dioxide for photosynthesis (anabolic)

• Metabolosomes → allows for higher concentrations of toxic molecules

• EUT: ethanolamine utilisation →           ethanolamine comes from the breakdown of cellular membranes so allows bacteria to use ethanolamine as energy and as a nitrogen resource

   

what is bet hedging behaviour

  decision needs to be made, certain cells do one thing and other cells do another and there is an overall advantage to the population

Most common way cells can divide

• Binary Fission

• get elongation then formation of septum and closes off 2 membranes

What is generation time

• the time required for a population of microbial cells to double

Other types of ways that cells can divide

  Budding division: a cell division process whereby new cell material is produced from a single point instead of along the entire cell

Growth phases

• Lag phase

• Exponential growth phase

• Stationary phase

• Death

Endosporulation

• examples are C . Difficile and Anthrax

• Common in soil

• spore are heat resistant,thick-walled, differentiated structure produced by certain gram-positive bacteria

• It is a survival strategy if run out of things then become a spore then later regrow again from that spore

• Spores are easily dispersed by wind, water, animal gut (faeces)

Process of Sporulation

• Cell forms ahrd tough later with DNA still intact

• Cell now refered ot as mother cell

• DNA condenses and lines up in middle of cell

• DNA divides and mother cell invaginates to form Forespore

• Mother cell then enguls spore so now has 2 membranes

• Then form active spore - resistant to envornmental conditions

• enzymes break down mother cell and spore released

What activates spore activation

spore heated for few minutes

what is Dipicolinic acid

• makes sure DNA is dehydrated and protected

• it is a substance unique to endospores that confers heat resistance on these structures

How many genes are spore specific

• 200 genes

when in favourable area

germination happens and forms cell again