microbiology

What is the role of genetic material?

-store information for the biochemical and structural components of the cell
-replicate to pass the information to the next generation
-generate genetic variation to provide diversity in the population

Genetics

the study of what genes are, how they carry information, how information is expressed, and how genes are replicated

Gene

A segment of DNA that encodes a functional product, usually a protein

genotype

all of the genes present in an organism

phenotype

physical characteristics of the organism based on the expression of their genes

genome

all of the generic material in a cell (coding and non-coding)

genomics

the molecular study of genomes

expression

genetic information is used within a cell to produce the proteins needed for the cell to function

recombination

genetic information can be transferred between cells of the same generation

replication

genetic information can be transferred between generations of cells

in DNA replication, the DNA is copied by

DNA polymerase

Leading strand in DNA replication is

synthesized continuously in 5' to 3' direction

Lagging strand in DNA replication is

synthesized discontinuously in small pieces known as Okazaki fragments

DNA replication is

semiconservative

What is semi-conservative?

each of the DNA molecules contains one parental and one new strand

gene expression

genetic information is used within a cell to produce the proteins needed for the cell to function

Transcription

describes the process by which RNA is made from a DNA template

How does transcription begin?

when RNA polymerase binds to the promoter sequence

Transcription only proceeds in the

5'\----3' direction

when does transcription stop?

when it reaches the terminator sequence

what produces a messenger RNA?

transcription

what are introns?

Introns are pre-mRNA molecules that have bits and pieces cut out of them before they go into action.

mRNA requires additional processing in Eukaryotes to remove

introns

Translation

the process of converting the info stored in the RNA into proteins

mRNA is translated into

codons (3 groups of nucleotides)

where does translation of mRNA begin?

start codon (AUG)

where does translation end?

stop codon (UAA, UAG, UGA)

What is a degenerate code?

several codons encode the same amino acid

messenger RNA (mRNA)

coding molecules translated into proteins

transfer RNA (tRNA)

involved in translation; charged with amino acids

ribosomal RNA (rRNA)

structural components of ribosomes

MicroRNA (miRNA)

various regulatory functions

in bacteria, the process of\______ and\______ can be coupled together

transcription, translation

what are constitutively expressed genes?

genes that produce protein all the time at a fixed rate

other genes which are expressed only as needed are either:

repressible genes or inducible genes

what is an operon?

a unit made up of linked genes that is thought to regulate other genes responsible for protein synthesis.

Repressor protein

a regulatory protein that binds to an operator and blocks transcription of the genes of an operon

what happens id lactose is present in an inducible gene expression?

it binds to and inactivates the repressor, allowing transcription to the lactose metabolism genes

repressible gene expression

gene is usually expressed, but transcription is blocked under certain conditions

inducible gene expression

gene is only expressed under certain conditions (transcription of mRNA only occurs under these conditions)

what are the three principal mechanisms

transformation, conjugation, transduction

Bacteria reproduce asexually so produce variation by what?

recombination

Griffith's experiment

genetic material could be transferred between dead bacteria and living bacteria

what happens during transformation?

DNA is released from dead bacteria is taken up by living bacteria

what happens if there is some similarity in the DNA sequences?

fragments can be integrated into the bacterial chromosome

what happens to this new genome?

it is passed onto the next generations

Bacterial conjugation

involves the copying and passing of a plasmid from a donor (F+) to a recipient (F-) cell

conjugative plasmids

contain genes encoding the pilus

What do plasmids often contain?

antibiotic resistance genes

Transduction

is the transfer of genes between cells by viruses

during transduction

-virus excision is not always perfect
-sometimes takes a piece of the bacterial genome with it
-this gets packaged into the virus particle
-it is injected into the next cell virus infects.

mutation

any change in the normal sequence of nucleotides in a piece of DNA

mutations can be

neutral, beneficial, or harmful

what are the three types of mutation?

missense, nonsense, frameshift

missense mutation

the change in the nucleotide alters the triplet codon thereby causing a different amino acid to be inserted into the growing protein

nonsense mutation

A mutation that changes an amino acid codon to one of the three-stop codons, resulting in a shorter and usually nonfunctional protein.

Frame-shift mutation

a mutation involving the addition or loss of nucleotides

spontaneous mutation rate

1 in 10^9 replicated base pairs or 1 in 10^6 replicated genes

mutagens

agents which increase the mutation rate

examples of mutagens

ultraviolet light, radiation, some chemicals

Pathogenicity

ability to cause disease. relates more to host damage

Virulence

the extent of pathogenicity. ability to cause disease but relates more to the ability of the microbe to cause disease

pathogenesis

development of disease

microbial reservoirs

natural habitat or host where a pathogen lives until it enters a new host

three types of microbial reservoirs

humans, animals (zoonosis), environmental sources (soil, water)

Zoonosis

An infectious disease that is transmissible from animals to humans.

portals of entry for microbials to get in:

-mucous membranes (most common)
-skin
-parenteral route (direct introduction into the tissues)

mucous membranes (microbes)

-respiratory tract (inhale)
-Gastro-intestinal (GI) tract (ingested)
-Genito-urinary tract (sexually transmitted)
-conjunctiva (eyes)

Skin (microbes)

-hookworm
-schistosomes (flukes)
- some fungi

Parenteral route (microbes)

-puncture of the skin: injections, surgical procedures (catheters)
-insect bites
-injury

first step of infection (or colonization)

attachment or adherence to host tissues

how do microbes bypass the immune system and host defenses?

-hiding (evading immune attack)
-disguising themselves (altering pathogen antigens)
-attacking (damaging host immune system)

hiding/evading host defenses

-capsules surround the microbe, protecting it from host immune system
- bacteria (streptococcus pneumoniae, klebsiella pneumoniae)
-fungi (cryptococcus neoformans)

disguising/altering pathogen antigens from host defenses

-changing surface proteins
-by mutation (HIV, influenza)
-by recombination (influenza, Trypanosoma)

how do pathogenic bacteria damage host cells?

-Directly: using essential host nutrients (iron). Lysis or damage due to replication
-Indirectly: penetration or exit from host tissues. producing toxins which are transported throughout the body causing widespread effects
-overgrowth

Toxin

a substance that contributes to pathogenicity

Toxemia

presence of toxin in the host's blood

Toxoid

Inactivated toxin used in a vaccine

Anti-toxin

antibodies against a specific toxin

Endotoxin

A toxic component of the outer membrane of certain gram-negative bacteria that is released only when the bacteria die.

exotoxin

a toxin released by a living bacterial cell into its surroundings.

endotoxins are

gram-negative, low on toxicity, and fever producing

exotoxins are

gram-positive, high in toxicity, and not fever producing

three main types of exotoxins

A-B toxins, membrane-disrupting toxins, and superantigens

A-B toxins

most exotoxins are of this type. two parts (A&B).
A: active part
B: binding part
Diphtheria toxin is an A-B exotoxin

Mycotoxins

toxins produced by fungi

Paralytic Shellfish Poisoning

shellfish eat dinoflagellates and accumulate saxitoxin, people will get sick when they eat the shellfish (red tides)

Pathogenic properties of Helminths

-Use host tissue for growth.
-The presence of parasite masses can interfere with host function.
-Parasite's metabolic waste can also cause disease symptoms.

portals of exit include

-respiratory tract (coughing and sneezing)
-gastrointestinal tract (feces and saliva)
-genitourinary tract (urine and vaginal secretions)
-blood (biting arthropods and needles or syringes)
MICROBES USUALLY LEAVE THROUGH THE SAME SYSTEM THEY ENTERED.

Pathology

study of disease

Etiology

study of the cause of disease

Pathogenesis

development of disease

Infection

colonization of the body by pathogens

Disease

An abnormal state in which the body is not functioning normally

Infection versus disease

A person can be infected or colonized with a microbe but have no sign of disease (ex: HIV-1)

Symptoms

a change in body function that is felt by a patient as a result of disease

Sign

A change in a body that can be measured or observed as a result of disease

Syndrome

A specific group of signs and symptoms that accompany a disease

communicable disease

a disease that is spread from one host to another (directly person to person)

Contagious disease

a disease that is easily spread from one host to another (measles)