Mikrobiologi 1

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• What are the main differences between prokaryotic- and eukaryotic cells? Prokaryotic cells are often smaller and have nucleiod where the DNA is based instead of a nucleus. Eukaryotic cells are usually bigger and have a nucleus that is enclosed by a membrane. Different DNA structure
• Virus VS cells Virus are a non living infectious agent that needs a host to replicate and survive. Cells are capable of growing on their own and can reproduce. Viruses are smaller than cells. The genetic material of cells are both DNA and RNA but in viruses it is either DNA or RNA and can not be both
• Capsule Polysaccharides or polypeptide layer. Assist with adhesion and prevent phagocytosis. Is a reservoir and helps the cells not to dry out.
• Cell wall Provides structural support and is mainly made of peptidoglycan. Protects against physical and chemical effects. Prevents osmotic lysis.
• Plasma membrane Selective barrier that separates the inside from the outside. Regulates transport in and out of the cell. Controls energy generation and selective permeability. Made of a phospholipid bilayer
• Porins Crosses the bacterial outer membrane and acts as a pore. They are proteins that are in the outer membrane of Gram- negative bacteria that forms channels. Allows passive diffusion of small molecules.
• Cytoplasm Cell- fluid and a gel-like matrix. Contains water, DNA, enzymes, ribosomes and waste- products
• DNA Is in the nucleoid region. Is usually a single circular chromosome.
• Plasmids Extrachromosomal DNA that usually contains 5- 100 genes. Encodes advantageous properties. Are moved via pili via conjugation. Plasmids are small circular or linear DNA molecules independent of the chromosome. Often encoded antibiotic resistance, virulence factors or metabolic traits. Carry non essential but advantegeous genes
• Ribosomes Synthesize proteins. Not the same structure in prokaryotes and eukaryotic.
• Flagellum Appendages to move in an aquatic environment. Helical propeller that allow motility, powered by proton motive force.
• Fimbriae Are used for attachment and are found on the surface in the different bacteria. Short numerous structures for adhesion.
• Pili There is F-pili and P-pili. Fertility pili are used to transfer plasmids (conjugation). Others are used by the bacterium to attach P-pili. Occur in Gram-Negative bacteria
• Nucleoid The aggregated mass of DNA that makes up the chromosomes of prokaryotic cells. A dense irregulary shaped region in prokaryotes where the chromosomal DNA is located. DNA is supercoiled and not membrane bound
• Describe in detail how a plasmid is moved from a donor- to a recipient cell. And what are plasmids 1. The donor cell that posseses F+ makes a sex pilus. 2. The sex pilus connects to the recipient cell that is not the F plasmid and pulls the two cells close together which is necessary when conjugation is happening. 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 recipient 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 others.
• What is passive transport (diffusion) and how does this differ from 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 concentrated to a region where it is less concentrated. Facilitate 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, requires no energy. Active transport- Primary active transport, secondary active transport, require energy. Bulk transport- Endocytosis and exocytosis, require energy.
• What is osmosis and what happens to a cell found in isotonic, hypertonic and hypotonic environments, respectively? Osmosis is a transport mechanism where diffusion of water across a selectively permeable membrane happens. In an isotonic solution nothing will happen because the solution is the same concentration of the solute in the cell. In a hypertonic solution, water will leave the cell and the cell will shrink. In hypotonic water will go into the cell and the cell will expand and can burst.
• Active transport Active transport is a movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins. This requires energy. Different types of pumps use this, like sodium potassium pump and proton pump
• Cell wall in prokaryotic cells The walls contain a polysaccharide called peptidoglycan that is composed of two modified glucose residues called N- Acetylglucoseamine (NAG) and N- Acetylmuramic acid (NAM). NAMs are linked by sorting polypeptides.
• Gram- positive VS Gram- negative Gram- positive have thick cell walls with 35-40 layers of peptidoglycan, a teichoic acid is present and has no outer membrane. Gram negative have a thin cell wall with 1-2 layers of peptidoglycan, an outer membrane with LPS and contains porins.
• What is LPS A lipopolysaccharide present in most Gram- negative bacteria. Have a complex lipid structure and uncommon sugar fatty acids. Has fatty acid associated that anchor LPS to the cell membrane and is strongly immune.
• Structure and function of LPS LPS increases the negative charge of the cell membrane and stabilizes the membrane structure. It consists of two components; the core polysaccharide and O-specific polysaccharide. It acts as a barrier to harmful molecules and triggers strong immune response.
• LPS in animal LPS has a layer called lipid A that is endotoxic which means it is toxic to animals. It can cause blood poisoning (sepsis)
• Slime VS capsule Capsule is firmly attached to the cell wall, it protects against phagocytosis and has a rigid structure. Slime is loosely attached, aids in biofilm and has an irregular structure
• Biofilm Biofilm is a natural way for different bacteria to grow. It consists of bacterial cells, polysaccharides, nucleic acids and proteins. A biofilm is formed when certain microorganisms adhere to the surface of some objects in moist environments and the microorganism start to reproduce. The microorganism form an attachment to the surface of the object with a slimy substance
• Advantages with biofil It can grow and form almost on any surface and a community can be formed by only a single microorganism.
• Gram-staining 1. Prepare a bacterial smear and apply a crystal violet to the smear for 1 minute. This will stain both Gram positive and negative. 2. Add iodine that binds to the crystal violet and this formes a large crystal violet- iodine complex inside the cell and this enhances the stains to remain inside the cell. 3 Decolorize with ethanol and rinse with water, this makes the Gram positive remain purple and the gram negative will be colorless. 4. Stain with safranin and rinse with water and let dry. This will have no effect on the Gram positive and it will turn the Gram negative pink/red.
• What is morphology The different, names shaped and arrangement prokaryotes have
• Coccus Spherical or oval. Singles, pairs, chains or clusters.
• Bacillus/rods Rod or cylinder. Single, pairs or chains
• Spirillum Spiral, curved or helical. Usually singles
• Vibration Curved. Usually singles
• Spirochete Thin, flexible and spiral-shaped with a helical structure. Singels
• Filamentous Long, thread like chains. Often branching structures
• Pleomorphic Change shape depending on environmental condition. Lack a rigid cell wall allowing them to get different shapes like cocci or filamentous
• Diplococcus two and two
• Tetrad four and four
• sarcinae eight and eight
• Streptococcus Chains
• Staphylococcus Bunches
• Single bacillus One and one
• diblobacilli two and two
• Streptobacili chains
• palisades Picked-fence
• Endospore Gram- positive bacilli can form endospores; they are a robust long living, highly resistant dominant structure. It is resistant to heat, UV, desiccation and chemicals. Formed under nutrient starvation
• Endospore formation and germination 1. The chromosome is replicated and 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 vegetative cells 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 consists for instance of keratin that makes the endospore extremely rough. 6. An outer spore-coat is formed and this increases its resistance to heat and different chemicals. 7. The endospore are released and the vegetative state goes through lysis
• Flagellar structure and movement Makes the bacteria motile to swimming. It is like a tiny rotating machine that functions to push or pull the cell through liquid. A helical structure and 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 Chemo is a direct movement of an organism toward or away from a chemical gradient. Away=negative chemotaxis. Toward=positive taxis

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