Microbiologi 1
Difference between prokaryotic and eukaryotic cells
The DNA structure and different organelles. Prokaryotic cells are often smaller and have a nucleoid. Eukaryotic cells are bigger and have a nucleus
Difference between cell and viruses
Virus are non living infections agents that needs a host to replicate and survive. Cells are capable of growing on their own and they can reproduce. Viruses are smaller. Cells can have both DNA and RNA. Virus can have either DNA or RNA not both in the same time
Capsule
Assist with adhesion and prevents phagacytosis. A reservoir and helps the cell not to dry out.
Cell-wall
Provides structual support and is mainly made of peptidoglygan. Protects against physical and chemical effects.
Plasma membrane
Barrier that seperates the inside from the outside. Regulates transport in and out of the cell.
Porins
Proteins that is in the outer membrane of gram-negative bacteria that form channels. It acts as a pore
Cytoplasm
Cell fluid. contains waterm DNA, enzymes, ribosomes and waste- products
DNA
Is in the nucleoid region, is usually a single circular chromosome. A double strand nucleic acid
Plasmid
Extrachromosal DNA that usually contains 5-100 genes. Encodes advatageous propeties. Are moved via pili via conjugation
Flagellum
Motility structure that can move in an aquatic environment
Fimbriae
Are used for attachmetn and are found on the surface in different bacteria
Pili
F-pili are used to transfer plasmid. Others are used by the bacterium to attach P-pili. Occur in Gram- negativ bacteria
Nucleoid
A region in prokaryotic cells that contains genetic material
How are plasmids moved?
1. The donor cell that posses F+ makes a sex pilus
2. The sex pilus connects to the recipent cell and pulls the two cells close togehter for conjugation.
3. A mating bridge forms between the two cells, allowing a direct connection for DNA transfer.
4 The F- plasmid in the donor cell is cut at a specific place and one strand of the plasmid DNA is transferred through the mating bridge to the recipient cell.
5. The recipent cell makes a complementary copy of the transferred plasmid DNA
6. The recipient cell that now has a full copy of the F plasmid becomes an F+ cell and is capable of donating plasmids to the others.
Passive diffusion vs facilitated diffusion
Diffusion is the random thermal motion of particles of liquid gases and solids. It results in the net movement of substances from a region where it is more concentraded to a region where its less.
Facilitated diffusion is the passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins
In which ways can transport across membranes occur?
Passive transport- Diffusion, facilitated diffusion and osmosis, no energy is needed.
Active transport- primary active transport and secondary active transport, need energy.
Bulk- transport- Endocytosis and exocytosis, need energy.
Osmosis
Transport mechanism where diffusion of water across a selectively permable membrane occur.
Isotonic solution
The concentration in the solution is the same as the concentration of the solute in the cell. Nothing will happen in this environment
Hypertonic
The cells solute concentration is higher than the inside of the cell, the solutes cannot cross the membrane.
Hypotonic
The cell will gain water faster than it will leave. The cell will swell and burst
Active transport
A movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins. This require energy. Different types of pumps use this like proton pump and sodium potassium pump
How is the cell wall of prokaryotes organized?
The walls contains the polysaccharide peptidoglycan that is composed of two modified glucose residues, N- acetylglucosamine (NAG) and N- acetylmuramic acid (NAM). NAMs are linked by polypeptides. If the peptidoglycan layer is thick with 20-80nm it is Gram-positive. If it is thin 2-7nm layers it is Gram-negative
What is LPS
Lipopolysaccharide present in most Gram- negative bacteria. Have a complex lipid structure and uncommon sugars and fatty acids. LPS increase the negative charge of the cell- membrane and stabilizes the membrane structure. It consist of two components, the core polysaccharide and O-specific polysaccharide.
Problems of LPS in animal
LPS has a layer called Lipid A that is endotoxic which means it is toxic to animals. It can cause sepsis.
Difference between slime and capsule
Capsule is firmly attached to the cell wall, the function is to protect against phagocytosis, has a rigid structure.
Slime is loosely attached to the cell wall, aids in biofilm, has a irregular structure
What is biofilm
Biofilm is a natural way for different bacteria to grow. It consists of bacterial cells, polysaccharides, nucleic acid and proteins. A biofilm forms when certain microorganisms adhere to the surface of some objects in moist environment and the microorgansims start to reproduce. The microorganisms form an attachment to the surface of the object with a slimy substance.
Advantage of biofilm
It can grow and form on almost every surface and a community can be formed by only a single microorganism
What are endospores?
Gram- positive bacilli can form endospore and they are a robust and long living.
What is morphology
Its the different shape, arrangement and names of prokaryotes .
Coccus
Spherical or oval. Single, pairs, chains or clusters
Bacillus/rod
Rod or cylinder. Single, pairs or chains
Spirillum
Spiral, curved or helical. Usually singles
Vibration
Curved. Usually single.
Spirochete
Thin, flexible and spiral- shaped with a helical structure. Singles
Filamentous
Long, thread like chains. Often branched
Pleormorphic
Change shape depending on environmental conditions, its the lack of a rigid cell wall thats allow it to cange
Diplococcus
Two and two
Tetrad
Four and four
Sarcinae
Eight and eight
Streptococcus
Chains
Staphylococcus
Bunches
Single bacillus
One and one
Diplobacilli
Two and two
Streptobacilli
chains
Palisades
Picked- fence
Describe endospores formation and germination
1. The chromosome is replicated, aligns alongside the cell. 2. The cytoplasmic membrane invaginates and a pre- spore is formed. 3. The cytoplasmic membrane grows and engulfs the pre-spore, the DNA of the vegatative cell is dissolved. 4. A cortex of calcium and dipicolinic acid is formed between the membranes, most of the water is removed from the cell. 5. A spore- coat is formed around the endospore, this consist for instance of keratin that makes the endospore extremely rough. 6. An outer spore- coat is formed and this increses its resistance to heat and different chemicals. 7. The endospores are released and the vegatative state goes through lysis
Flagellar structure and movement
Makes the bacteria motile to swimming. Are like a tiny rotating machine that functions to push or pull the cell through liquid. Are a helical structure. The main part is called filaments and they are composed of many copies of the protein flagellin. A wider region at the base of the filament is called a hook. This connects the filaments to the flagellum motor in the base
Chemotaxis and phototaxis
Chemotaxis: Direct movement of an organism toward or away from a chemical gradient. If it goes towrd it is positve chemotaxis and if it goes away it is a negative chemotaxis.
Phototaxis is the movement of an organism toward light