Omtenta mikrobiologi
What is spirochetes?
spirochetes are thin and long bacteria
How does staphylococcus form?
Staphylococcus form grape-like clusters during growth
What is the structure of spirochaetes?
Sprirochaetes have a very long and twisted structure
What are bacilli
Some bacteria are rod-shaped and these bacteria are called bacilli
Pleomorphic
Some bacteria are pleomorphic, which means that they have no special shape when they are studied using a light microscope
Virion
The extracellular form of a virus is called a virion and this is the structure by which a virus is transferred between cells. A virion is extracellular. Virions always have a nucleic acid and a capsid
Defenition of viruses
Viruses are classified as obligate intracellular parasite.
How do you classify viruses
The primary way to classifying viruses is to divide them into DNA-RNA and retroviruses
Spikes
Spikes helps the virion attach to its host-cell
Prions
Prions are proteins that can change the structure of some other proteins
Infection
Infection means that virion/virus enters a cell
What protects th virol genome
The viral genome is protected by a protein-cover named capsid
Virus and cancer
Some virus can cause cancer
What cause lysis
Some naked viruses can cause lysis of the host-cell if they are able to reach the cells nucleus
Latent infections
In latent infections, the virus stay dormant in the cell and no virions are produced
What happens in the lytic phase
In the lytic phase new virions are released from the host-cell through bacterial lysis
Biofilm
The biofilm structure prevents the penetration of toxic molecules. In a biofilm the cells structure are not easily flushed away. Within a biofilm, channel are formed through which nutrients can flow and it is natural for bacteria to grow as biofilm
Bacterial capsule
A bacterial capsule helps pathogenic bacteria to adhere to different tissues and organs and prevents the cell from drying out. The bacterial capsule acts as a reservoir for polysaccharides and a bacterial capsule is a polysaccharide-layer outside the cell-wall.
Gram positive vs negative
A gram positive cell-wall contains more peptidoglycan than gram negative
LPS
LPS is a molecule that consists of a lipid A, unusual sugars and fatty acids.
Gram negative
A gram negative cell consists of a membrane, a cell wall of peptidoglycan and an extra cell-membrane
Gram positive
Some gram positive bacteria can form endospores
Cell-membrane
The cell membrane is a selective barrier and consists of phospholipids and blocks the transport of some molecules that are toxic for the cell
Plasmids
Plasmid are extrachromosomal DNA, and contains less genes that the chromosome. Natural occuring plasmids are almost always made of double-stranded DNA
Endospores
An endospore can survive a temperature of 100 degrees, reasons for bacteria to form endospores are alterled oxygen levels and lack of nutrients
Autotrophic bacteria
Autotrophic bacteria use carbon dioxide to build their cellular structure
Lithotrophic bacteria
Lithotrophic bacteria use inorganic compounds as electron donors
Phototrophic organisms
Phototrophic organisms can convert sunlight into chemical energy.
Reduction potential
Reduction potential is a measure of the tendency of a chemical species to gain electrons
Aerobic respiration
In aerobic respiration glucose is broken down into carbon-dioxide and water and carbon-dioxide is the final electron acceptor.
Anaerobic bacteria
Some anaerobic bacteria use sulphate as the final electron acceptor and an anaerobic respiration of an electron transport chain is required
How do bacteria form acetic acid
Some bacteria can convert ethanol into acetic acid
Structure of archea
The membrane structure of archaea differs from bacterial membrane structure. The cell-wall lack peptidoglycan and nucleus. Archaea multiply through binary fission
do the lag phase lack ATP?
At least during parts of the lag-phase the bacteria lacks ATP
What happens during the stationary phase of growth
During the stationary phase of growth, bacteria produce secondary metabolism
death phase
During death-phase the number of viable cells decreases
How do bacteria multiply
Bacteria multiply through binary fission
Which temperature is the best for human pathogens
Most human pathogens multiply at the highest rate at a temperature of 37 degrees
Defined media
In defined media the exact composition of chemicals is known.
Selective media
A media that contains compounds that selectively inhibit growth of some microorganisms are called selective media.
Enriched growth media
Enriched growth media is supplemented with specific growth-factors to improve growth of specific organisms
What happens with macromolecules at high temperature
At a very high temperature, virtually all macromolecules denature
Filtration sterilization
Filtration through a membran filter does not remove all types of microorganisms.
Radiation sterilization
Radiation can be used to sterilize objects that do not tolerate water
What happens with phage-DNA during the lysogenic-phase
During the lysogenic-phase, phage-DNA integrates within the bacterial chromosome by recombination becoming prohage
Where is phage-proteins made
New phage-proteins are produced in the lytic-phase
what does the normal flora do?
The intestinal normal flora synthesize important vitamins
Transient flora
Transient flora can sometimes turn into the normal flora.
How do we now the earths age?
The age of earth has been estimated by studying radioactive isotopes found in old rocks
First forms of life
It is believed that the first forms of life were not cells but single stranded RNA
Endosymbiotic hypothesis
The endosymbiotic hypothesis provides an explanation for the origin of organelles in the eukaryotic cell and the origin of chloroplats
Early earth atmosphere
The early earth had no atmosphere of oxygen meaning that the surface was bombarded by meteors
How old is the earth
Around 4.54 billion years ago
Waters existent
Evidence support that water existed arounf 4,3 billion years ago
First phototrophic organism
The first phototrophic organism that evolved were anoxygenic
How long have bacteria existed
Fossils have been found that strongly indicate that bacteria existed 3,5 billion years ago
what shares the same biochemical properties
The bacteria that belong to the same microbial species share the same biochemical properties
Phylogenic tree
A phylogenic tree is a diagram that depicts the evolutionary history of an organism
What is a bacterial species made of?
A bacterial species is made up of one to several bacterial chains
How is bacterial familys groups
Bacterial families are according to taxonomic heirarchy grouped into orders
Operon
An operon consists of a set of genes controlled by the same promoter
Fermentation test
In fermentation tests bacteria are incubated with growth media, a pH-indicator and the specific carbohydrate of interest. If the pH-indicator of the fermentation test is phenol red it will turn yellow if the test becomes positive. Fermentation allows bacteria to proceed the glycolysis by oxidizing NADH and NAD+
SIM-test
One thing that is investigated when performing a SIM-test is if the bacteria produce hydrogen sulphide
Urease-test
The pH-indicator in a urease test will change color if positive due to the bacterial production of ammonia when breaking down urea
Oxidase-test
If an oxidase-test turns positive, this means that the bacterium contains cytochrome C oxidase
Catalase enzyme
To test if bacteria has the catalase enzyme they are placed in a drop of hydrogen peroxide, if bubbles are formed the test is positive
How is spores stained
Spores can be stained using malachite green
Counter stain cells
In order to counter stain cells during Gram-staining safranin can be used
Alpha hemolytic
If there is a green zone around a bacterial colony when growing on blood-agar plates the bacterium is alpha-hemolytic
Direct test
To determine bacterial species based on morphology and biochemical analyse in an example of a direct test. Both rowing organisms from a sample on specific bacterial growth-media and determining the species based on morphology and biochemical analyses and trying to identify the DNA of the organism using PCR is an example of direct test
Indirect test
To identify antibodies species for a certain organism in blood and to identify toxins from a non-organism is an example of an indirect test
Quick test
Must maximally take 30 minutes, is often based on antibodies species to the agent of interest. A quick test must be able to performed wihout advanced machines and only have an maximum of 2 reagents
Bacterial cell wall
The bacterial cell wall is composed of two sugar-derivatives that in short are called NAG and NAM, the cell-wall consists of peptidoglycan
Cytoplasm
The cytoplasm contains mailny of water and contains of bacterial waste-products
Chromosome in bacteria
Bacteria usually have single cirkular chromosome
Flagellum
Some bacteria have a flagellum that helps bacteria to move in an aquatic environment
Fimbria
Fimbria are appendages that can help the bacteira to adhere to different tissues and organs
Extremophiles
Thrive in habitats which for other terrestrial life-forms are intereble hostile or even lethal
Mathanogens
Produce methane as a metabolic by-product
Fixing nitrogen gas
It is a high energenic cost of fixing nitrogen gas
Defenition of bacterial growth
Bacterial growth is defined as an increase in cell mass or an increase in the number of cells
Time of growth
The time required for bacteria to divide depend on evironmental factors
Do bacteria need water
All bacteria require water to grow
Human pathogens
Human pathogen are usualy mesophilic bacteria
Chemostat
Using a chemostat, the growth rate of the bacteria can be controlled by altering the concentration of a limiting nutrient. By using a chemostat bacteria can be grown in a stetady state and then growth occurs at a specific growth rate. In continous growth using a chemostat, the bacteira is forced to exponential growth
Primary pathogens
Primary pathogens are not normally associated with the host
Asymptomatic carrier
An asymphtomatic carrier does not have detactable symptoms
Pathogens classification
Pathogens can sometimes also be classified as normal flora
Taxonomy
Taxonomy is partly about to classify bacteria
Microbial species
Bacteria that belong to the same microbial species share the same biochemical properties
Sigma factor
A sigma factor has to bind to the RNA-polymerase before the polymerase can bind to the promoter
Transcription and translation
In prokaryotic transcription of a gene and translation of corresponding mRNA can occur simtaneously
Open reading frame
An open reading frame is a DNA sequence between a start and a stop codon
Genome assembly
Genome assembly is partly about putting sequenced fragments together in correct order.
Sanger sequencing
Sanger sequencing is still used as sequening method
Conjugation
Conjugation means that a recipient cell recevies a plasid from a bacterial donor
Transformation
Transformation means that a bacterium pick up DNA from the environment
Transduction
Transduction means that bacterial viruses are moving pieces of DNA from a donor to a recipient bacteria
Negative staining
Negative staining can be performed in order to determine if the bacteria are encapsuled
What happens in gram staining
When bacteria are gram stained they will achive different colors due to differences in the bacterial cell-wall
Gram reaction
Gram reaction is a primary system of classify bacteria
MALDI-TOF
In clinical microbiology,MALDI-TOF is odten used to determine the causing bacterial pathogen in an unknown species.
PCR
PCR is a method used to amplify specific DNA regions of organisms
E,coli in urine
E,coli can convert nitrate to nitrite when growing in urine
Bacteria in bladder
If the zone detecting presence if leukocytes is strongly positive the person who the urine comes from proably has bacteria in the bladder
Kiry bauer test
A common method to determine if bacterium is resistant to a certain type of antibiotic is the kirby bauser test.
Resistant bacteria
Bacteria that do not show a growth inhibition zone are resistant to the antibiotic tested