micro exam 2!

cell tropism

preference for a specific cell type

what are some of the cell characteristics that is needed for virus to select certain cell types to infect?

cell receptors for virus

cell transcription factors that recognize viral promoters and enhancer sequences

ability of cell to support virus replicaion

physical battiers

local temp, pH, O2 tension enzyme and non-specific factor in body secretions

digestive enzymes and bile in the gastrointestinal tract that may inactivate some viruses

direct cell damage and death (4)

diversion of cell's energy, shut off of macromolecular synthesis, competition of viral mRNA for ribosomes, and competition of viral promoters and transcriptional enhancers for cellular transcription factors such as RNA polymerases, and inhibition of the interferon defense mechanisms

indirect cell damage (4)

integration of the viral genome, induction of mutations in the host genome, inflammation and hot immune response

which host system is ultimately responsible for how the viral disease will be resolved?

HIV

a virus that attacks and destroys the human immune system

human immunodeficiency virus (AIDS virus)

obtained through anal or vaginal sex, or sharing needles, syringes, or other drug injection equipment (for example, cookers)

what is the target cell of HIV

- CD4+ T cell
- HIV destroys these cells; the body can replace these cells but overtime the ability of HIV to destroy CD4 cells exceeds the body's ability to replace the cells

What does HIV do?

Destroys TH cells, depresses cell-mediated immunity

influenza

flu, transmitted through salvia.

target cells of influenza

primarily target airway epithelial cells via α2,3- and α2,6-type receptors, but the distribution of these receptors in many species is uncertain and may be a significant factor influencing infection

dengue

fever, rash, and headache. Positive Herman's sign

transmitted by Aedes mosquitos which reside in water-filled containers

what is the target cell of dengue

monocytes, but not T or B cells, are the principal target cells for dengue virus (DV) infection among human peripheral blood mononuclear cells.

prions

infectious protein particles that do not have a genome

can be inherited (Chromosome 20). accumulate in cells and cause disease

target cells of prions

Mast Cells. Mast cells have been implicated in prion pathogenesis due to their high expression levels of cellular prion protein (PrP or PrPC) and their ability to traffic to the brain

what do prions cause

transmissible spongiform encephalopathies

an airy neurodegenerative disease in humans and animals

PrPC

normal cellular prion protein, on the cell surface

PrPsc

scrapie protein; accumulates in brain cells, forming plaques

PrPsc causes

PrPC protein to change its conformation to abnormal form

newly produced PrPSC molecules convert...

more normal molecules to the abnormal form through unknown mechanism

prion formation

bacterial growth curve

lag phase, log phase, stationary phase, death phase

lag phase

"flat" period of adjustment, enlargement; little growth

cell synthesizing new components, and varies in length

What does the lag phase depend on?

Depends on the media used, history of inoculum used (inoculated or not), and the specific organism. If cells are coming from one media to the same, no lag phase. If cells are coming from a rich media to a defined media, lag phase

exponential phase

-also called log phase
-rate of growth is constant and maximal
-population is most uniform in terms of chemical and physical properties during this phase

stationary phase

period of equilibrium; microbial deaths balance production of new cells

closed systme

population may cease to divide but remain metabolically active

possible reasons for stationary phase

-nutrient limitation
-limited oxygen availability
-toxic waste accumulation
-critical population density reached

death phase

population is decreasing at a logarithmic rate

what causes the death phase

-the severe depletion of nutrients
-accumulation of waste products

long term stationary phase

the phase following the death phase of a growth curve in which the population size remains at a more or less constant low level for an extended period.

enzymes necessary to control toxic oxygen products

catalase enzymes break down hydrogen peroxide (H2O2) to water and oxygen molecules, which protects cells from oxidative damage by reactive oxygen species. commercial catalases are produced from Aspergillus niger through a solid-state fermentation process

Biofilm characteristics

form on surfaces in aquatic systems, resistant to biocides, composed of organic and inorganic constituents, release organisms in bulk fluid

can be formed on any conditioned surface and are ubiquitous in water naturally

bacterial cell cycle as compared to eukaryotic cell cycle

cell division is simpler in prokaryotes than eukaryotes because prokaryotic cells themselves are simpler. prokaryotic cells have a single circular chromosome, no nucleus, and few other cell structures. eukaryotic cells, in contrast, have multiple chromosomes contained within a nucleus, and many other organelles.

role of FtsZ

form a ring along with other proteins embedded in the cell membrane, then expand radially inward, pinching the cell into two new cells

forms Z ring

role of MinCDE

MinCDE system in E.Coli limits Z ring to cell center. MinC, MinD, and MinE osciliate from one side of cell to other. high concentration of MinC at poles prevents formation of Z ring at those locations

role of Mre B and where it is found

MreB is a protein found in bacteria that has been identified as a homologue of actin, as indicated by similarities in tertiary structure and conservation of active site peptide sequence

specific gene products and the roles they take in chromosome partitioning and cell wall biosynthesis

replisome pushes, or leads to condensation of daughter chromosomes to opposite ends. ParA/ParB proteins in C. crescenus

bactoprenol

carrier molecule that plays major role in insertion of peptidoglycan precursors

role of bactoprenol in peptidoglycan synthesis

peptidoglycan monomers are synthesized in the cytosol of the bacterium where they attach to a membrane carrier molecule called bactoprenol. the bactoprenols transport the peptidoglycan monomers across the cytoplasmic membrane and helps insert them into the growing peptidoglycan chains

cardinal condition

the primary or major symptom by which a diagnosis is made. the major condition of the virus

oxygen requirements of bacteria

Aerobic - requires presence of oxygen

Anaerobic - requires absence of oxygen

Facultative Anaerobes- can grow with or without oxygen but prefers oxygen.

Microaerophilic - prefers less oxygen than the levels found in the atmosphere. 2-10% O2

obligate anaerobe: usually killed in presence of O2

errotolerant anaerobes: grow with or without O2

types of culture media

chemically defined, complex, reducing, selective, differential, enrichment

Defined (synthetic) media

all components and their concentrations are known

complex media

contain some ingredients of unknown composition and/or concentration

selective media

suppress unwanted microbes and encourage desired microbes

differential media

allows growth of several types of microbes and displays visible differences among those microbes

selective media example

EMB/MacConkey agar/ Sabourauds/Salmonella Shigella.

differential media examples

blood agar, motility medium

therapeutic dose

drug level required for clinical treatment

purpose of Kirby-Bauer test

antibiotic sensitivity testing is used to determine the susceptibility of bacteria to various antibiotics

3 types of drug resistance

intrisnic
acquired
drug-tolerant

drug-tolerant bacteria (persisters)

lack the mechanisms for antibiotic resistance and "ignore" the presence of antibiotics, usually because they are embedded in biofilms that antibiotics cannot effectively penetrate or are growing too slowly to be inhibited.

Acquired drug resistance

occurs when there is a change in the genome of a bacterium that converts it from one that is sensitive to an antibiotic to one that is resistant

Intrinsic drug resistance

bacteria must be resistant to any antibiotic that they themselves produce

sterilants

destroy all microorganisms, including endospores

disinfectants

Chemical products that destroy all bacteria, fungi, and viruses (but not spores) on surfaces.

antiseptics

Chemical germicides formulated for use on skin; registered and regulated by the Food and Drug Administration (FDA).

sanitizers

agents that reduce microbial numbers to a safe level but do not completely eliminate all microbes

bacteriostatic

inhibits bacterial growth

Bactericidal

kills bacteria

Bacterolytic

destruction or dissolution of bacterial cells

name some ways other than chemical means in which we are able to control microorganisms (3)

physical methods
biological methods
genetic methods

Physical methods of microbial control

Heat
Filtration
Low Temperatures
High Pressure
Desiccation
Osmotic Pressure
Radiation

biological methods of microbial control

antibiotics
using other microorganisms to control the growth of pathogens

genetic methods of microbial control

using genetic engineering to create modified organisms that can control pathogens

what are some characteristics that makes a drug toxic?

what is the action of Tamiflu

This is a sialic acid analogue that binds to neuraminidase, so viral release is inhibited

the proposed mechanism of action of oseltamivir is via inhibition of influenza virus neuraminidase with the possibility of alteration of virus particle aggregation and release

what antimicrobials are used to control or inhibit fungus, viruses and parasites?

intrinsic drug resistance

bacteria must be resistant to any antibiotic that they themselves produce

acquired drug resistance

occurs when there is a change in the genome of a bacterium that converts it from one that is sensitive to an antibiotic to one that is resistant

drug-tolerant drug resistance

bacteria (persisters) lack the mechanism for antibiotic resistance and "ignore" the prescene of antibiotics, ususally because they are embedded in biofilms that antibiotics cannot effectively penetrate or are growing too slowly to be inhibited

Mechanisms of Drug Resistance

-exclusion of drug
the drug can't bind to or penetrate pathogen
-pump drug out
-inactivation of the drug
chemical modification of drug by a pathogen
-alteration of target enzyme or organelle
-use of alternative pathways or increased production of the target metabolite

Detecting Drug Resistance

Commercial gene expression systems are designed to identify the production of specific resistance factors, such as a target-modifying enzyme

Several test systems measure the color change induced when a chromophore is acted upon by either a β-lactamase or an antibiotic-modifying enzyme
a) Color changes are measured spectrophotometrically and protein concentration is extrapolated from a standardized curve

Detection systems are also commercially available to identify genes encoding drug resistance factors using polymerase chain reactions (PCRs)

common antifungal drugs

-imidazoles
-other antifungals

Treating Superficial Mycoses

For example, Candida

Topical and oral

Disrupt membrane permeability and inhibit sterol synthesis

Disrupts mitotic spindle; may inhibit protein and DNA synthesis

Treating Systemic Mycoses

Difficult to control and can be fatal
Three common drugs...

3 common drugs to treat systemic mycoses

amphotericin B - binds sterols in membranes
5-flucytosine - disrupts RNA function
fluconazole
low side effects, used prophylactically

antifungal drugs

polyenes and azoles, target plasma membrane of fungi

Is it easier to treat superficial mycoses or systemic infections?

superficial mycoses

identifying targets for anti-hiv drugs

anti-HIV drugs

reverse transcriptase inhibitors, protease (integrase) inhibitors, fusion inhibitors

nonucleoside reverse transcriptase inhibitors (NRTI's)

drugs that bind to sites on the reverse transcriptase within the cell cytoplasm, preventing RNA- and DNA-dependent DNA polymerase activities needed to carry out viral DNA synthesis; prevents the transfer of information that allows the virus to replicate and survive

Integrase (protease) inhibitors (PI's)

Prevent the incorporation of the HIV genome into the host's chromosomes

fusion inhibitors

prevent viruses from successfully fusing with the host cell

Anti-HIV drugs work by

Inhibiting the reverse transcriptase enzyme

metabolism is the Toal of all chemical reactions in the cell and divided into 2 parts

catabolism and anabolism

catabolism

-fueling reactions
-energy-conserving reactions
-provide ready source or reducing power (electrons)
-generate precursors for biosynthesis

anabolism

the synthesis of complex molecules in living organisms from simpler ones together with the storage of energy; constructive metabolism.

anabolism vs catabolism

anabolism (building up) and catabolism (breaking down)

what is a cell process that is both anabolic and catabolic

respiration!

aspects of metabolism common to all organisms (6)

(1) life obeys the laws of thermodynamics.
(2) the energy cells obtain from their environment is most
often conserved as ATP.
(3) -oxidation-reduction (redox) reactions play a critical role in energy conservation.
(4) the chemical reactions that occur in cells are organized into pathways.
(5) each reaction of a pathway is catalyzed by an enzyme or a ribozyme.
(6) the functioning of biochemical pathways is regulated.

exergonic reaction

a spontaneous chemical reaction in which there is a net release of free energy
delta G is negative

endergonic reaction

a non-spontaneous chemical reaction in which free energy is absorbed from the surrounding
delta G is positive

standard free energy change

the change in free energy that will occur for one unit of reaction if the reactants in their standard states are converted to products in their standard states

Role of ATP in metabolism

exergonic breakdown of ATP is coupled with endergonic reactions to make them more favorable

phosphate transfer potential

-ATP is said to have a HIGH phosphate transfer potential
-It readily sends a phosphate group to other molecules
-Other molecules have higher phosphate transfer potential than ATP
-ATP \= ADP and the phosphate from those molecules

oxidation-reduction (redox) reactions

electrons are transferred from one reactant to another

standard redox potential

-equilibrium constant for an oxidation-reduction reaction
-a measure of the tendency of the reducing agent to lose electrons

standard redox potential - negative Eo

better electron donor

standard redox potential - more positive Eo

better electron acceptor

the greater the difference between the Eo of the donor and the Eo of the acceptor...

the more negative the deltaG0'