Microbial Nutrition, Growth, & Control Study Guide

A comprehensive set of flashcards covering critical concepts from microbial nutrition, growth, cell division, genetics, and control measures in microbiology.

What is the most common mechanism for bacterial cell division?

Binary Fission

List the four steps of binary fission.

1. Elongation of the cell, 2. Replication of the chromosome, 3. Separation of the chromosomes into the two parts of the cell, 4. Formation of septum (Cytokinesis).

Define 'Origin of replication'.

Where replication begins.

How many Origins of replication do bacterial chromosomes have?

One.

What is Cytokinesis?

The division of the cell into two via formation of a cross wall between the two daughter cells.

Define Penicillin-binding protein (PBP).

Group of proteins that hydrolyze bonds in existing peptidoglycan strands and link together new strands.

What are N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)?

Major components of peptidoglycan that bind to a membrane protein called bactoprenol.

Define Autolysins.

Degrade polypeptide where new units are to be added; new NAM-NAG units can then be inserted into the peptidoglycan layer.

What is crescentin?

A homologue of eukaryotic intermediate filaments.

What are the other forms of asexual reproduction?

Budding, Baeocyte formation, Spore formation.

Define Budding.

Budding off daughter cells; seen in Listeria monocytogenes.

Define Baeocyte formation.

Multiple rounds of cell division; seen in Cyanobacteria.

What is Spore formation?

Form multinucleoid filaments that divide to produce spores with a single nucleus.

List and define each phase of the Bacterial Growth Curve.

1. Lag Phase: No net growth as bacteria adjust, 2. Log Phase: Highest rate of division, 3. Stationary Phase: Stable number of viable microorganisms, 4. Death Phase: Decrease in viable microorganisms, 5. Long-term Stationary Phase: Variants come and go.

What is generation time (GT)?

The time it takes for the population to double.

When is it best to calculate GT?

Log phase.

True or False: Cells typically exist in aqueous conditions.

True.

Define hypertonic and hypotonic.

Hypertonic: Higher concentration of solutes; Hypotonic: Lower concentration of solutes.

If a cell is in a hypertonic solution, it will ___; in a hypotonic solution, it will ___.

Shrink; Burst.

What are the three distinct cardinal growth temperatures for organisms?

1. Minimum growth temperature, 2. Maximum growth temperature, 3. Optimal growth temperature.

Define Halophiles.

Grow best in extremely salty environments.

Define Xerophiles.

Grow best in dry conditions.

Define Psychrophiles.

Grow between 0C and 20C - refrigeration temperatures.

Define Mesophiles.

Grow between 20C and 45C.

Define Thermophiles.

Grow between 55C and 85C.

Define Hyperthermophiles.

Grow between 85C and 113C – usually archaens.

Define Aerobe.

Grow in presence of atmospheric oxygen.

Define Obligate Aerobes.

Require oxygen for growth and die without it.

Define Anaerobe.

Grow in absence of oxygen.

Define Obligate Anaerobes.

Cannot survive in presence of oxygen.

Define Facultative Anaerobes.

Grow better with oxygen than without it.

Define Barotolerant.

Survive increased pressures.

True or False: Most human pathogens are Mesophiles.

True.

When does food spoilage occur?

When nutritional value, texture, or flavor changes due to spoilage organisms.

True or False: Only a select few foods contain spoilage microorganisms.

False; all foods do.

What are the three most common food spoilage organisms?

Bacteria, yeasts, and molds.

How is food spoilage controlled?

By manipulating temperature.

Define the term sessile.

Microorganisms that grow attached to a surface rather than floating freely.

What do sessile microorganisms form?

Biofilm: a complex of slime-enclosed colonies that stick to each other.

Why is a mature biofilm described as an 'ecosystem on its own'?

It has a heterogenous community of microorganisms differing in metabolic activity.

True or False: Biofilms only form on non-living surfaces.

False; they can form on living surfaces.

What is Quorum Sensing?

Bacteria coordinate expression of genes based on population density.

Define and rank these terms from most to least biocidal: Antisepsis, Disinfection, Sanitization, Sterilization.

1) Sterilization: removal of all viable microorganisms, 2) Disinfection: killing or inhibiting organisms, 3) Sanitization: removing populations to safe levels, 4) Antisepsis: preventing infection of living tissue.

A - ___ agent is one that kills microorganisms.

Cidal; for example, Bactericidal.

A - ___ agent inhibits the growth of microorganisms.

Static; for example, Bacteriostatic.

___ populations take longer to kill than ___ populations.

Larger; Smaller.

True or False: Overall death rate decreases as the population gets smaller.

True.

Filtration techniques allow scientists to selectively remove microbes based on their ___.

Size.

What microorganism are membrane filters not able to remove?

Viruses.

Name an example of an air filter.

Surgical masks and cotton plugs.

What are the two physical control methods that destroy microorganisms?

Heat and Radiation.

Define moist-heat sterilization.

Exposure to heat above 100C destroys viruses, fungi, and bacteria; example is Autoclave.

What is Pasteurization?

Treating heat-sensitive beverages below boiling points; examples are milk and beer.

Define dry-heat sterilization.

Requires higher temperatures to oxidize cell constituents; example is incinerators.

What is ionizing radiation?

Gamma radiation destroys bacterial endospores and sterilizes items.

What is ultraviolet radiation used for?

Causes thymine dimers for surface sterilization.

Pasteurization ____ spoilage by reducing the number of organisms, but does not sterilize.

Slows.

True or False: Ionizing radiation is effective against all microorganisms.

False; not always effective against viruses.

What UV wavelength is the most bactericidal?

260 nm.

What is chemotherapy?

The use of chemicals to kill microorganisms or inhibit their growth within host tissue.

Define and provide an example of phenolic disinfectants.

Denature proteins and disrupt membranes; example is Orthocresol.

What are alcohols used for?

Dissolve membrane lipids and denature proteins.

What are halogens?

Important examples are Iodine and Chlorine.

What are heavy metals?

Once used as germicides, they inactivate proteins.

What are quaternary ammonium compounds?

Antimicrobial detergents that denature proteins and disrupt membranes.

What are sterilizing gases?

Ethylene oxide gas that kills microbes and spores; used for heat-sensitive materials.

Why are heavy metals not commonly used today?

They have a high degree of toxicity.

What is an antimicrobial detergent?

An organic cleansing agent with both hydrophilic and hydrophobic components.

What are the two most important alcohol germicides?

Ethanol and Isopropanol.

What factors influence the efficiency of antimicrobial agents?

Concentration of agent, duration of exposure, temperature.

What is the genetic material?

DNA.

Define a genome.

The entire set of DNA present in a cell or virus.

What is the difference between genotype and phenotype?

Genotype: specific sets of genes; Phenotype: observable characteristics.

What three ways did Frederick Griffith demonstrate transformation?

1. Living encapsulated cells to mice (died), 2. Living non-encapsulated and heat-killed encapsulated (lived), 3. Both types led to death.

What is transformation?

The ability of organisms to take up DNA from the environment.

True or False: DNA and RNA are nucleic acids.

True.

What is the structure of a nucleotide?

A pentose sugar attached to nitrogenous base and phosphate group.

What bond binds nucleotides?

Phosphodiester bonds.

What are the four differences between DNA and RNA?

1. DNA has deoxyribose, RNA has ribose, 2. DNA has Thymine, RNA has Uracil, 3. DNA is double stranded, RNA is single stranded, 4. RNA has larger functions.

What is a pyrimidine? Name them.

Nitrogenous bases with one ring structure: Cytosine, Thymine, Uracil.

What is a purine? Name them.

Nitrogenous bases with double-ring structures: Adenine, Guanine.

What is the role of mRNA?

Carries genetic information to ribosome for protein synthesis.

What is the role of tRNA?

Carries specific Amino Acids to growing polypeptide chain during translation.

What is the role of rRNA?

Structural component of ribosomes that may act as a catalyst.

True or False: DNA strands run parallel to each other.

False; they run antiparallel.

True or False: Covalent bonding is stronger than Hydrogen bonding.

True.

How far does a single turn of the helix stretch?

About 3.4 nm and consists of 10 base pairs.

What results in major and minor grooves in DNA?

Asymmetrical spacing of DNA backbones.

What does Chargaff's rule state?

Amount of Guanine equals Cytosine; amount of Adenine equals Thymine.

True or False: DNA with more Adenine and Thymine bonds is more stable.

False; G and C bonds are more stable.

True or False: Proteins are polymers of nucleic acids.

False; they are polymers of amino acids.

What is the structure of an amino acid?

Central alpha carbon surrounded by an amino group, a carboxyl group, and a variable side group (R).

What is a peptide bond?

Covalent bonds between amino acids formed by dehydration reaction.

What direction does polymerization occur in?

From N terminal to C terminal.

Define Transcription.

Information from DNA is transferred to mRNA in the nucleus.

Define Translation.

Ribosomal complex attaches to mRNA to form a polypeptide.

Recall central dogma.

DNA -> RNA -> Protein.

True or False: DNA replication is conservative.

False; it's semi-conservative.

Describe the three types of replication models.

1. Conservative model: One old, one new DNA molecule. 2. Semi-conservative model: Each has one new and one old strand. 3. Dispersive model: Mixture of old and new DNA.

What is the molecular complex that carries out DNA replication?

Replisome.