Bacteria and archaea

What are the components of a prokaryote

No nucleus

Non membrane bound organelles (mitochondria/ chloroplast/ ER/ Golgi)

Has 70S ribosomes (50s +30s)

Diverse metabolism> enzymes located in cell membrane and cytoplasm

Respiratory chain in plasma membrane

Transport systems in cell membrane involved in movement of solutes across membranes

replicate with binary fission

Steps of binary fission

1- Cell chromosomes replicates

2-Chromosomes attract to either pole

3-membrane starts pulling

4-Septum forms

5-Separation

-plasmids replicate independently

How to measure cell mass

-Measure optical density of bacteria culture using a spectrophotometer to pass light at 600nm through a microbial suspension.

-The higher the cell density, less light is transmitted to detector.

Name given to an organism which energy source is from sunlight

Phototroph

Name given to an organism which energy source is from chemicals (inorganic/organic compounds)

Chemotroph

Name given to an organism which electron source is from organic compounds (i.e. sugars)

Organotroph

Name given to an organism which electron source is from inorganic compounds (I.e. iron/hydrogen sulphide)

Lithotroph

Name given to an organism which carbon source is from CO2

Autotroph

Name given to an organism which carbon source is from organic compounds (i.e. sugars)

Heterotrophs

What is the only photosynthetic prokaryote that produced O2 (photolithoautotrophs)

Cyanobacteria

What is E-coli metabolism wise

Chemoorganheterotroph

What is a niche

 set of environmental conditions in which a species of microbe can replicate

What conditions determine where a microbe can live

-Nutrient availability

-Oxygen concentration

-Temperature

-pH

-Solute concentration (osmolarity) and water activity

-Pressure

-light intensity

-radiation

What does it mean if a prokaryote is free-living

-Inhabits every type of environment on earth

-Has a wide range of metabolic capabilities

-May benefit from syntropy (metabolic by products of others)

What is meant by pathogenic

Interactions with host organism and causes host damage

What is it meant by mutualistic

Interactions with host organism whereas both partners benefit

What is meant by commensal

Interactions with host organism where one partner benefits and hosts are unaffected

What is meant by Parasitism

one organism gains (“parasite” / “pathogen”) and the other is harmed (“host”)

Can be extracellular or interacellular

What is meant by amensalism

negative impact of one organism on another, based on release of a specific compound (e.g. toxin)

What is it meant by competition

When two organisms try to acquire or use the same resource

What is a biofilm-microbial community

communities of microbes firmly attach to surface with aid of extracellular polymeric substances matrix

What is a mature biofilm

a complex, dynamic community of microorganisms

What is heterogeneity

differences in metabolic activity and locations of microbes

How does heterogeneity work in biofilms

-Interactions occur among the attached organisms

-exchanges take place metabolically, DNA uptake and communication

What does the nucleoid do in prokaryotes

-Location of chromosome and associated proteins

-Usually not membrane bound (few exceptions)

-Usually 1 closed circular, double-stranded DNA molecule

-Supercoiling and nucleoid proteins (different from histones) aid in folding

What do plasmids do in prokaryotes

-They are extrachromosomal DNA found in bacteria, archaea, some fungi

-usually small, circular double-stranded DNA molecules

-Can also be inherited or replicated during replication

-Carry accessory genes that can give bacteria an advantage under particular environmental conditions

What are some advantages of accessory genes

-Conjugative →enable DNA transfer between bacterial cells

-Resistance →provide resistance to antibiotics or other antimicrobials

-Bacteriocin →produce compounds that kill or inhibit competing bacteria

-Virulence →carry genes that enhance colonisation or disease

-Metabolic →enable degradation or use of unusual compounds

What does bacterial cell walls have

-Rigid structures outside the plasma membrane

-Maintains bacterial cell shape

-Protects the cell from osmotic lysis and some toxic substances

-contains peptidoglycan

What is peptidoglycan

mesh-like polymer of repeating subunits arranged in long strands

What is a gram positive cell wall and its components

Type of bacterial cell wall

Composed primarily of a thick layer of peptidoglycan

Many contain teichoic acids, which contribute to -ve charge of cell surface

Lipoteichoic acids extend through the peptidoglycan and are anchored in the plasma membrane (stability)

-Teichoic acids can contribute to cell wall structure and interactions with the environment….e.g. adhesion to host cells

Some Gram-positive bacteria have a surface layer of proteins associated with the peptidoglycan

What is a gram negative cell wall and its components

More complex than the Gram positive cell envelope

-Contains a thin layer of peptidoglycan surrounded by an outer membrane

-Outer membrane contains phospholipids, proteins, lipoproteins and lipopolysaccharide (LPS) > has no teichoic acids

-Outer membrane acts as a selectively permeable barrier  , restricting entry of many toxic substances

-Porins allow diffusion of small hydrophilic molecules across the outer membrane

Space between the inner and outer membranes containing peptidoglycan and various proteins =periplasm