Microbio exam 2

Chromosomes

Most condensed form of DNA

DNA packaging

DNA is organized into chromosomes

Eukaryotic chromosomes

Linear DNA structures (multiple per cell, 46 in humans)

Prokaryotic chromosome :

Single circular DNA molecule

DNA function

Codes for RNA and proteins

Central dogma

DNA → RNA → Protein

Genome

All DNA regions that are expressed into functional products

Gene

DNA sequence that codes for a protein

Noncoding DNA

DNA that does not code for proteins (~99%)

Gene expression

Process of converting DNA into functional proteins

Transcription

DNA → RNA

Translation

RNA → amino acid sequence (protein)

Operon

Group of genes controlled by a single promoter

Promoter

DNA region where transcription begins

Structural genes

Genes that code for proteins

Operator

Regulatory DNA region controlling gene expression

Prokaryotic gene regulation

Often organized in operons

Polycistronic mRNA

One mRNA molecule codes for multiple proteins

monocistronic mRNA

One mRNA molecule codes for one gene

Bacterial mRNA

Usually polycistronic

RNA polymerase

Enzyme that synthesizes RNA from DNA

Initiation (transcription)

RNA polymerase binds to the DNA promoter

Elongation (transcription) :

RNA polymerase converting DNA into mRNA

Termination (transcription)

RNA polymerase detects terminator sequence and transcription stops

Phenol-soluble modulins (PSMs)

Toxins produced by S. aureus

PSM peptides

Short proteins that destroy host cells

Operon (S. aureus)

Gene cluster controlling toxin production

Eczema / Atopic dermatitis

Skin condition caused by bacterial toxins

Bacteremia

Bacterial infection in blood

Pneumonia

Lung infection caused by bacteria

Antibiotic resistance

Ability of bacteria to survive antibiotics

Cause of resistance

Mutations and horizontal gene transfer

Selective pressure

Environmental force that favors certain traits

Misuse of antibiotics

Major contributor to resistance

MRSA

Methicillin-resistant Staphylococcus aureus

mecA gene

Gene responsible for methicillin resistance

Horizontal gene transfer (HGT)

movement of genes between cells of same generation [no replication for DNA change and is fast]

MRSA origin :

First found in hospitals in the 1960s

Rapid replication

Bacteria divide quickly (~20 min)

Genetic variation :

Increased by mutations and HGT

Microbial evolution

Continuous adaptation for survival

Inactivating enzymes

enzymes once inside is modified and makes it ineffective

Efflux pumps

enzymes once inside are flushed out

Decreased uptake

structure of cell stopping antibiotic from getting inside

Drug target alteration

target site is change so antibiotic cant bind

Mutation

Permanent change in DNA sequence

Spontaneous mutation

Error during DNA replication

Mutagen-induced mutation

are environmental agents that brings about mutation [physical, chemical, biological]

Base substitution (point mutation)

Is a single incorrect nucleotide replacing the initial nucleotide

Frameshift mutation

Is a deletion or insertion of nucleotides most likely to change protein sequences

Silent mutation [synonymous]

nucleotide substitution results in no amino acid change

Missense mutation

nucleotide substitution results in amino acid change

Nonsense mutation

Produces a stop codon

Mutagen

Agent that causes DNA mutation

Physical mutagens

Radiation (UV, X-rays)

Chemical mutagens

can intertwine with DNA to cause changes or mismatching during DNA synthesis

Biological mutagens

Viruses altering DNA

Ionizing radiation

Causes double-strand DNA breaks

Non-ionizing radiation (UV)

Causes thymine dimers

Bromouracil

Thymine analog causing mispairing

DNA mispairing

Incorrect base pairing during replication

HPV (Human papillomavirus)

Virus causing mutations

Cervical cancer (HPV) :

~99% linked to HPV

Fungi

Diverse group of organisms (~150,000 species)

Fungal diversity

Wide variety of forms and functions

Decomposers

Break down organic matter

Fungi in health

Can be beneficial or harmful

Largest fungus

~3.5 square miles in Oregon

Malheur National Forest

Location of largest fungus

Penicillin

Antibiotic derived from fungi

Alexander Fleming

Discovered penicillin

1920s discovery :

ime period of penicillin discovery

Cordyceps

Parasitic fungi infecting arthropods

Cordyceps species

400+ types

Fungal pathogens

Fungi that cause disease

Life characteristics Vs viruses

Metabolism, reproduction, growth, response, evolution

Viruses

Do not meet most criteria of life

Non-living (viruses)

Cannot reproduce or metabolize independently

Intracellular parasite (virus)

Requires host cell to reproduce

Plasma membrane (virus)

Absent unless envelope present

Binary fission

Not used by viruses

Ribosomes (virus)

Absent

ATP metabolism (virus)

Absent

Antibiotics

Do not affect viruses

Interferon sensitivity :

Viruses are affected

Nucleic acid (virus)

DNA or RNA (never both)

Viral genome types

Single or double stranded

Single or double stranded

Protein shell surrounding nucleic acid

Envelope

Lipid membrane (some viruses)

Spikes

Structures for host cell attachment

Viral enzymes

Help replication inside host

Virus size

Very small compared to cells

Host specificity

Infect specific organisms

Tissue specificity

Target specific tissues

Polyhedral virus

Geometric virus shape

Virus morphology

Organized and structured

bacterial transcription

RNA Polymerase turns DNA into mRNA