Diversity and Biology of Bacteria Flashcards
Bacteria are
Single celled, without a nucleus
We are interested in bacteria because
they play a role in our body and form what we call the . microbiome (1-3% of our body weight)
Tuberculosis is a disease where
1.7 million people die from the disease each year and is one of the top 10 causes of death worldwide
Bacterial meningitis is
an infection of the brain?
Bacterial infections can also be…
foodborne (e.g. salmonella, camplyobacter)
The nucleoid is…
a double stranded circle bacterial chromosomes
Bacteria contain 70S ribosomes which contain…
30S and 50S subunits. These are major targets for antibacterial drugs
50S RNA is a piece of RNA which…
have conserved parts and some diverse parts?
Bacteria can also have plasmids which are…
Circular or linear extrachromosomal DNA’s not usually essential for cell survival. Capable of autonomous replication (able to replicate independently).
Plasmids are needed in bacteria for…
Preventing from being attacked by antibodies, and the plasmid usually encodes for proteins which aid in the invasion of host cells.
Shigella spp is a….
Human specific pathogen which can cause an acute intestinal infection. This occurs from fecal oral transmission. The bacteria can replicate in macrophages and is therefore able to evade the immune response.
Cell membrane of bacteria is…
fairly similar to mammals in structure, and have various functions such as electron transport and energy production.
Cell wall is a…
Rigid layer around the cytoplasmic membrane - this resists osmotic pressure.
bacteria is classified
according to their cell wall characteristics. Gram Strain is an example of this.
If you have bacteria, you can fix it onto organ cells, and stain the cells.
By doing so, you will find 2 different results to show gram positive or negative.
The difference between gram positive and gram negative bacteria is
gram negative have 2 layers of membranes and between the layers are lipoprotein and peptidoglycan. Gram positive is where the lipoprotein and peptidoglycan is exposed and is not between any layer.
A peptidoglycan is
a complex of sugars with side chains of amino acids.
It is designed to protect the cell wall and is rigid in shape. Peptidoglycans are recognised by the immune system. Some bacteria can change their peptidoglycan composition, our immune system may not detect the bacteria as before.
Teichoic acids are…
chains of glycerol phosphate/ ribitol phosphate. They are bound covalently to peptidoglycan
Gram negative bacteria have…
a much more complex cell wall. They also have a thinner peptidoglycan than gram positive.
Lipopolysaccharides are
essential for bacterial viability. The hydrophilic O polysaccharide repels hydrophobic molecules.
Porins allow…
The uptake of small hydrophilic molecules.
The S- layer is…
frequently found on the surface of gram positive and gram negative cells. The s layer functions are a cell wall biogenesis and the control of cell divison
Capsules are…
amphorous polysacharride slime around cells. It prevents the recognition of the bacteria by the immune system. Several genes encode the capsules.
The flagella
Provides motility and is attached via hook and basal body containing motor proteins and switch proteins (control direction of rotation)
Flagella is recognised by
the innate immune system (H- antigen) and they express antigenic and strain determinants and are a ligand for a pathogen pattern receptor to activate innate immune response
Pili and fimbriae are
Protein spikes that extend from the surface. Pili are longer and more rigid than the fimbriae. Fimbriae are although more abundant.
What is a potential function of fimbriae?
To allow E coli to bind to the urethra
There are many different classes of pili varying based on
Structure and function. They are used to attach to surfaces, promote biofilm formation and antigens
External Structures - pili
sex pillus is involved in DNA transfer in conjugation
Why study bacterial metabolism?
Phenotype based identifcation - substrate utilization and growth inhibitors, and determination of metabolic activity
Bacterial replication is essential for transmission as…
It identifies nutrient requirements and pathway bottlenecks (microbial pathogenesis)
Nutritional factors include
Macronutrients (Carbon being main element), growth factors, and micronutrients (iron, boron e.t.c)
Nutrient acquisition/ transport occurs via
Passive transport, or active transport.
Passive transport occurs via
simple diffusion e.g. small hydrophobic molecules
Facilitated diffusion e.g. hydrophobic molecules req….
Proton symports are
Driven by electrochemical transmembrane proton gradient
Co- transport in same direction, hence, symport
Example of such is Lactose permease in E.coli
ABC transport is..
ATP binding cassette. It is a form of active transport. Hydrolysis of ATP drives transport. Specific binding proteins involved
Group Translocation is…
substrate modified, generally phosphorylated, during transport, e.g. phosphotransferase system.
The energy is provided by the PEP passed along chain of enzymes
Glucose transport systems
Bacteria can encode for different systems depending on the needs of the bacteria and the area in question
Catabolism is where
Amino acids, monosaccharides and glycerol+ fatty acids are broken down into simpler products to form energy
E.coli has….
transcription factors which enact to cause certain genes to transcribe.
Listeria spp
are gram positive rods, and come from natural human habits such as soil, dust e.t.c.
Listeria is engaged in cell- cell spread
This is to avoid extracellular defences. This is why cystosolic replication occurs.
Energy generation happens due to…
the production of ATP and NADH
Respiration occurs via..
the proton gradient which is used to power ATP synthase to subsequently produce ATP
Aerobic Respiration is where
oxygen is involved
Anaerobic respiration is where
Nitrate is reduced to nitrite via nitrate reductase (in the context of bacteria)
Mycobacterium tuberculosis is where
the bacteria enters the phagosome but manipulates the phagosome so that a lysosome is not formed and it is not degraded.
Host cell lipids are an essential carbon source during infection. It can switch from a carb based metabolism to a fat based metabolism
These bacteria can also survive under energetically unfavourable condition and poorly oxygenated conditions
Bacterial Growth is…
the increase in the number of cells, not the size of a single bacterium. This occurs by binary fission.
Binary fission occurs via…
- elongation of cell wall, membrane, and cell volume
2. Chromosome duplication
Fts proteins
interact to form a divisome, a cell division apparatus
A divisome….
forms the septal ring and defines the cell division plane
There are different types of Fts proteins, such as,,,
ftsl - for peptidoglycan biosynthesis
ftsk - responsible for chromosome separation
min proteins are
cytoskeletal proteins that are coiled in poles. They form a bipolar gradient that help to localise the ring
The bacterial cell cycle is highly regulated….
with steps occuring such that:
- G1
- S-phase
- G2
Bacterial cell cycle can be controlled via…
Nutritional control - whereby starvation can lead to replication and growth and fast growth leads to division.
Effect of the stress…
results in regulated proteolysis by Lon. If there is no stress, DNAa is able to conduct replication, however, when there is a heat shock for example, the DNAa and any unfolded protein is broken down to avoid any reeplication
Endospores can be formed….
when the bacteria is triggered due to adverse conditions, and the mother cell secretes a protein coat (calcium dipicolinate) to protect then lyses…….
Spore forming bacteria include….
botulism, tetanus, anthrax
A generation time for bacteria is..
the time required to complete fission cycle from parent cell to 2 daughter cells.
Requirements for growth include
Temperature (death above the maximum temperatures comes from enzyme inactivation), pH (5-8 being the optimum usually), oxygen
Listeria monocytogenes is a…
food borne pathogen, facultative anaerobe, can grow in temps between 0 and 45 degrees, it can tolerate high salt concentrations
helicobacter pylori…
colonises the human stomach (1.5-3.5), causes acute gastritis and several ureases, it has flagellum which gives its ability to move around to areas which are not as acidic, and release bicarbonate and ammonia which are of higher pH to mask itself,
