Microbiology Exam 2

Part of Ch. 6, 7-9, and 13-14

Cytopathic Effects (CPEs)

Microscopic or macroscopic degenerative changes or abnormalities in host cells and tissues. The observable change that occurs in cells as a result of viral replication.

Virulent Phage

One reproductive choice of viruses, multiply immediately upon entry, lyses the bacterial host cell at the end of viral life cycle.

Temperate Phage

Bacterial and archaeal viruses that can establish a lysogenic relationship, rather than immediately lysing their hosts. Have 2 reproductive options:

1. Reproduce lytically as virulent phages do

2. Remain within the host cell without destroying it (lysogeny)

Changes the phenotype of the host → bacteria become immune to superinfection, phage may express pathogenic toxin or enzyme.

Lysogeny

The state in which a viral genome remains within a bacterial or archaeal cell after infection and reproduces along with it, rather than taking control of the host cell and destroying it.

Tumor

A growth or lump of tissue; benign tumors remain in place while malignant can travel throughout the body.

Neoplasia

Abnormal new cell growth and reproduction due to loss of regulation

Metastasis

Spread of cancerous cells throughout body

Cancer

Occurs when cells begin to divide uncontrollably due to certain genetic events.

It is estimated that viruses cause up to 25% of all cancers.

Protooncogene

Genes that promote healthy cell growth and division.

Oncogene

Mutated versions of oncogenes that can lead to uncontrolled cell growth and cancer.

Kaposi’s sarcoma

A rare type of cancer that affects the blood vessels and lymph nodes. It is caused by the human herpesvirus 8.

Bethesda system

Reports findings from Pap smears, which screen for cervical cancer.

Hemagglutination assay

A laboratory technique used to detect and quantify viruses and other pathogens that can agglutinate (clump) red blood cells.

Plaque Assay

A technique used to quantify the concentration of infectious viruses in a sample.

Viroids

An infectious agent that is a single-stranded RNA not associated with any protein; the RNA does not code for any proteins and is not translated.

Satellite virus

Subviral infectious agents are composed of DNA or RNA encapsidated with the aid of an unrelated helper virus. Nucleic acid only → needs helper virus b/c they do not encode structural components.

Hepatitus D

A liver infection caused by the Hepatitis D virus. It is a satellite virus that requires the presence of the hepatitis B virus to replicate and spread.

Prion (PrP)

An infectious agent consisting only of protein; prions cause a variety of spongiform encephalopathies such as scrapie in sheep.

Templating

Where a misfolded, infectious prion protein (p-PrP) acts as a template to convert normal cellular prion proteins (c-PrP) into the misfolded, disease-causing form. Like alpha-helices to beta-pleated sheets.

Spongiform encephalopathy

Degenerative central nervous system diseases in which the brain has a spongy appearance; due to prions. Ex: Mad Cow Disease, Kuru, Scrapie, etc.

v. Creutzfeldt-Jakob disease

A rare, fatal brain disorder linked to consuming meat from cattle infected with bovine spongiform encephalopathy, also known as “mad cow disease”.

Replisome

A large protein complex that copies the DNA double helix to form two daughter chromosomes.

Septation

Formation of a cross wall between two daughter cells during cell division.

FtsZ

A tubulin homologue that compiles the Z ring, which is essential for bacterial cytokinesis (cell division). Positions peptidoglycan synthesis enzymes for septum growth.

Divisome

A collection of proteins that aggregate at the region in a dividing microbial cell where the septum forms.

Photoautotroph

An organism that uses light energy, an inorganic electron source (H₂O, H₂, H₂S), and CO₂ as its carbon source.

Chemoautotroph

An organism that takes inorganic chemicals and transforms it into energy.

Photoheterotroph

Organisms that use light energy but cannot use carbon dioxide as their sole carbon source.

Penicillin-binding Proteins (PBPs)

Link peptidoglycan strands and catalyze controlled degradation for new growth.

Autolysin

PBP enzymes that degrade peptidoglycan at site where new units are added.

MreB

A bacterial protein homologous to eukaryotic actin that is essential for maintaining the rod shape of many bacteria by forming dynamic filaments beneath the cell membrane, which coordinate the placement of new cell wall material. Helical polymerization throughout the cell (homologue of actin) determines cell diameter/elongation as the Z ring forms.

Crescentin

Intermediate filament homologue localizes to the short, curved side of the cell, and asymmetrical cell wall synthesis forms a curve.

Chemoheterotroph

An organism that uses organic compounds as sources of energy, electrons, and carbon for biosynthesis.

Obligate Aerobe

Organisms that grow only in the presence of oxygen.

Obligate Anaerobe

Microorganisms that cannot tolerate oxygen and die when exposed to it.

Aerotolerant Anaerobe

Microbes that grow equally well whether or not oxygen is present.

Catalase

An enzyme that catalyzes the destruction of hydrogen peroxide.

Superoxide Dismutase

An enzyme found in all aerobes, facultative anaerobes, and microaerophiles that catalyzes the conversion of the radical oxygen species superoxide to hydrogen peroxide and molecular oxygen (O₂).

Nitrogen fixation

The metabolic process in which atmospheric molecular nitrogen (N₂) is reduced to ammonia, carried out by nitrogen-fixing bacteria and archaea.

Trace elements

Nutrients required in very small quantities for growth and reprodution.

Growth Factors

Organic compounds that must be supplied in the diet for growth because they are essential cell components or precursors of such components, and cannot be synthesized by the organism.

Optimum growth temperature

Psychrophile

A microorganism that has an optimum growth temperature of 15°C or lower and a temperature maximum around 20°C.

Mesophile

A microorganism with a growth optimum around 20 to 45°C, a minimum of 15 to 20°C, and a maximum of about 45°C or lower. These cause the most diseases causing organisms, human body regulates at 37°C.

Thermophile

A microorganism that can grow at temperatures of 55°C or higher; the minimum is usually around 45°C.

Hyperthermophile

A microbe that has its growth optimum between 85 and about 120°C. They usually do not grow well below 55°C.

Neutrophile

A microorganism that grows best at a neutral pH range between pH 5.5 and 8.0. Most bacteria and protists are this. They exchange potassium for protons.

Acidophile

A microorganism that has its growth optimum between about pH 0 and 5.5.

Alkaliphiles (Alkalophiles)

A microorganism that grows best at pHs from about 8.5 to 11.5.

Culture Media

Nutrient-rich preparations that provide essential nutrients, water, energy sources, and growth-promoting factors for microorganisms and other cells in a laboratory setting.

Binary Fission

Asexual reproduction in which a cell separates into two identical daughter cells.

Generation time

The time required for a bacterial cell to grow and divide.

Arithmetic growth

A constant increase in cell numbers per unit of time.

Logarithmic (exponential) growth

A population growth pattern where a population initially grows exponentially but then slows down and levels off as it approaches the carrying capacity of its environment due to limiting factors like space, food, or predation.

Lag phase

A period following the introduction of microorganisms into fresh culture medium which there is no increase in cell numbers or mass during batch culture.

Log phase

The phase of the growth curve during which the microbial population is growing at a constant and maximum rate, dividing and doubling at regular intervals.

Stationary Phase

The phase of microbial growth in a batch culture is when population growth ceases and the growth curve levels off.

Decline Phase

The final stage is where the death rate exceeds the reproduction rate, leading to a decrease in the number of viable cells.

Sterility

All life-forms have been completely removed from some material

Disinfection

Reducing the number of pathogenic organisms on objects or in materials so they pose no threat of disease

Antiseptic

Chemical agent applied to tissue to prevent infection by killing or inhibiting pathogens

Sanitization

Reduction of the microbial population on an inanimate object to levels judged safe by public health standards.

Pasteurization

The process of heating liquids to destroy microorganisms that can cause spoilage or disease.

Bacteriostatic

Inhibiting the growth and reproduction of bacteria.

Bactericidal

The ability of a substance, surface, or biological agent to kill bacteria.

Microbial death rate

Describes the speed at which microorganisms die when exposed to a lethal agent, like a disinfectant or heat.

Decimal reduction time

The time it takes to kill 90% of organisms or endospores in a sample at a specified temperature.

Filtration

The passage of a material through a filter or other straining device.

Debridement

The removal of damaged tissue or foreign objects from a wound.

Autoclave

An apparatus for sterilizing objects by the use of steam under pressure.

Ultra-high temperature

A food processing method that rapidly heats food to temperatures over 135°C to kill microorganisms and spores, extending shelf life significantly without refrigeration.

Radiation

1. Ultraviolet

   a) 260nm (UV-C) wavelength is most effective

   b) Doesn’t penetrate materials well

   c) Results in the formation of thymine dimers

   d) Useful for water treatment

2. Ionizing Radiation

   a) 0.1-40nm

   b) damages DNA and produces peroxides, including endospores, but not as effective against viruses

   c) Used to treat plastics, food & medicine

Phenols

Function as antiseptics and disinfectants that inhibit microbial growth by denaturing proteins and disrupting cell membranes.

Alcohols

Used as disinfectants and antiseptics due to their ability to denature proteins, disrupting microbial cell membranes and rendering cells inactive or dead. They are effective against a broad range of microbes, but they do not destroy bacterial spores. Stronger at lower concentrations (down to 50%).

Halogens

Known for antimicrobial properties, acting as disinfectants and antiseptics. They achieve this by oxidizing and destroying cellular components like proteins, nucleic acids, and cell membranes, disrupting critical processes such as oxidative phosphorylation. When added to phenols increases phenol effectiveness.

Chlorine

Oxidizes cell components, kills many types of bacteria, and inactivates viruses; it is easily inactivated by organic material, its gas and bleach form are sporicidal.

Iodine

Oxidizes cell components and iodinates proteins, harmful to people with iodine or even seafood allergies, takes several minutes to act, and does not sterilize the skin. Typically used in Betadine surgical scrub, in concentrations of 3-5%, destroys fungi, amoebas, virus, and most bacteria, but not endospores.

Oxidizing agents

A chemical substance that accepts electrons from microbial cells, causing oxidation and leading to the disruption of cell membranes, denaturation of proteins, and damage to DNA, ultimately killing or inactivating the microorganisms.

Surfactants

Molecules that disrupt microbial membranes and are used as antimicrobials in disinfectants. Important for clearing away organic material, effectiveness is greatly enhanced by mechanical scrubbing action, the easiest and cheapest means of preventing the spread of disease.

Silver

Usually toxic and inactivates proteins. Silver nitrate was used as drops in a baby’s eyes to prevent gonococcal infection.

Mercury

Thimerosal (Eli Lilly’s merthiolate), usually seen as a vaccine preservative

Selenium

Selenium sulfide kills fungi and their spores, used in dandruff shampoos

Copper

Has antimicrobial properties; this type of plumbing has a huge impact on maintaining water quality.

Aldehydes

Disrupts the structure of both proteins and nucleic acids, sporicidal but can cause cancer

Glutaraldehyde

Kills spores and sterilizes equipment exposed to it for 10 hours.

Formaldehyde

Formaldehyde inactivates viruses and toxins without destroying their antigenic properties.

Ethylene oxide

Used for heat & moisture-sensitive equipment.

Antibiotics

A microbial product or its derivative that kills susceptible microorganissm or inhibits their growth.

Synthetic

Antimicrobial drugs that are synthesized by chemists

Semi-synthetic

Antimicrobial drugs that are derived from naturally occuring substances and extracted from microbes.

Natural

Antimicrobial drugs that are produced straight from microbes.

Therapeutic dose

The drug level required for clinical treatment

Toxic Dose

Drug level at which drug becomes too toxic for patient (produces side effects)

Therapeutic Index

The ratio between the toxic dose and the therapeutic dose of a drug, used as a measure of the drug’s relative safety.

Selective Toxicity

The ability of a chemotherapeutic agent to kill or inhibit a microbial pathogen while damaging the host as little as possible.

Beta-lactams

Referring to antibiotics with a β-lactam ring (Penicillins and cephalosporins). They irreversibly bind to the enzyme that cross-links NAM subunits.

Penicillin

A β-lactam antibiotic. The first true antibiotic to be discovered and used clinically. Discovered by Alexander Fleming in 1928. Naturally occuring = narrow spectrum, semi-synthetic froms = broader spectrum.

Bacitracin

A polypeptide antibiotic used to inhibit the cell wall synthesis of Gram-positive bacteria, particularly Staphylococcus and Streptococcus species.

Isoniazid

Antibiotic used to treat tuberculosis → inhibits the synthesis of mycolic acids in the bacterial cell wall, leading to bacterial death.

Ethambutol

An antimycobacterial drug with a narrow spectrum of activity, primarily affecting the cell wall synthesis of Mycobacteria. Bacteriostatic → stops bacteria from multiplying that kills them outright.