Microbio Exam 2

Cell Cycle

The complete sequence of events extending from the formation of a new cell through the next cell division

Septum

A partition that forms during cell division to divide two daughter cells

Exponential growth

When a growing bacterial population is doubling at regular intervals

Generation Time (Doubling times)

The time it takes for a microbial population to double in number

Origin of Replication

The site at which replication begins

Replisome

DNA synthesis machinery

Partitioning System

ParB binds parS sites on the daughter chromosomes. A gradient of ParA proteins directs the complex of ParB/parS to the opposite pole of the cell in a relay mechanism

Cytokinesis

Formation of two daughter cells following cell division

Septation

Formation of a cross wall between two daughter cells

FtsZ (tubulin homologue)

Forms contractile ring during septum formation (bacteria and archaea)

Nucleiod Occlusion

Coordinates chromosome movement and cell separation

Elongasome

Molecular machine that synthesizes the peptidoglycan of rod shaped cells

Batch Culture

Incubated in a closed vessel with a single batch of medium

Lag Phase

When microorganisms are introduced into fresh culture medium, usually no immediate increase in cell number occurs. Not a time of inactivity, rather cells are synthesizing new components

Exponential Phase

Microorganisms grow and divide at the maximal rate possible given their genetic potential, the nature of the medium, and the environmental conditions

Stationary Phase

When essential nutrients is depleted, population growth slows and eventually stops

Death Phase

During this phase, the equilibrium between dying and reproducing cells shifts and the number of viable cells declines exponentially at a constant rate

Long-Term stationary phase

Can last months to years. During this phase, the bacterial population continually evolves so that actively reproducing cells are those best able to use the nutrients released by their dying brethren and best able to tolerate accumulated toxins.

Growth rate constant (k)

Number of generations per unit of time

Extremophiles

Grow under harsh conditions that would kill most other organisms

Halophiles

salt loving. Requires the presence of NaCl at a concentration above about 0.2 M

Osmotolerant

Microorganisms that can grow over wide ranges of water activity but optimally at higher levels

Xerotolerant

Can withstand either high solute concentration ps or the effects of desiccation.

pH

A measure of the relative acidity of a solution

Acidophiles

Grow best between pH 0 and 5.5

Alkaphiles

Grow best between pH 8 and 11.5

Neutrophiles

Grow best between pH 5.5 and 8

Psychrophiles

0°C to 20°C

Psychrotrophs

0°C to 35°C

Mesophiles

20°C to 45°C

Thermophiles

45°C to 85°C

Hyperthermophiles

85°C to 100°C

Obligate Aerobe

Requires oxygen

Obligate anaerobe

Dies is the presence of oxygen

Microaerophile

Requires 2% to 10% oxygen. Only tolerated low oxygen levels

Facultative anaerobes

Does not require oxygen, but grows best in the presence of oxygen

Aerotolerant anaerobes

grows equally well in presence or absence of O2

Barotolerant

Adversely affected by increased pressure, but not as severely as nontolerant organisms

Peizophilic (barophilic)

requires high pressure for growth

Eutrophic

Nutrient rich environments

Oligotrophic

Environments with low nutrient levels

Growth arrest

Environmental conditions with a lack of nutrients or deviation from optimal

Viable but not culturable state

Transient inability to grow under conditions that previously permitted growth.

Persisters

Identified by their ability to survive exposure to an antibiotic even though they do not harbor antibiotic resistance genes

Sessile

Biofilms on surface

Planktonic

free floating

Biofilm

Slime encased communities of microbes

extracellular polymeric substance (EPS)

a glycocalyx that helps cells in a biofilm attach to their target environment and to each other

biofilm matrix components can include:

Polysaccharides, proteins, glycoproteins, glycolipids, DNA

emergent properties

Properties that could not be predicted from studying its component single cells

Quorum sensing

A way of assessing size of a microbial population

N-acylhomoserine Lactone (AHL)

an autoinducer molecule produced by many gram negative organisms

Culture medium

Solid or liquid mixture of nutrients and other compounds needed to grow, transport, and store microorganisms in the lab

Defined (synthetic) media

Each ingredient can be defined with a chemical formula

Complex media

Contain some ingredients of nonspecific chemical composition

Agar

Sulfated polymer solidifying agent

Supportive media

Sustain growth of many types of microorganisms

Enriched media

Encourage growth of fastidious microbes

Selective media

Allow the growth of particular microorganisms while inhibiting the growth of others

Differential media

Distinguish among different groups of microbes and even permit tentative identification of microbes based on their biological characteristics

pure (axenic) culture

A population of cells arising from a single cell

Enrichment culture

A tool used to encourage the growth of microbes having particular characteristics, while at the same time inhibiting the growth of other microbes

Culturomics

An approach to solve problems by formulating many types of media and incubate those media in many different conditions

Direct counts

Using a count chamber to count square by square

colony forming unit (CFU)

term used to define the cell or group of cells that produces a colony when transferred to plated media

binary fission

The cell elongates as a new cell envelope material is synthesized. The nucleiod must be replicated and partitioned into each half of the elongated cell.

autoinducer

signaling molecules that are produced in response to changes in cell-population density

Antibiotic

Natural products or their derivatives that kill susceptible microbes or inhibit their growth

Antimicrobial Agent

Agent that kills or inhibits the growth of microorganisms

Paul Ehrlich

Developed the concept of selective toxicity

Identified dyes that effectively treated African sleeping sickness

Sahachiro Hata

Worked with Ehrlich

Identified arsenic compounds that effectively treated syphilis

Penicillin

First antibiotic to be discovered

Selective Toxicity

Ability of a drug to kill or inhibit pathogen while damaging host as little as possible

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Therapeutic Index

Ratio of toxic dose to therapeutic dose

The larger the index, the better the chemotherapeutic agent in general

Narrow-Spectrum Drugs

Effective only against a limited variety of pathogens

Broad-Spectrum Drugs

Target many different kinds of bacteria

Cidal Agent

Kills the target pathogen

Static Agent

Reversibly inhibits growth of microbes

Minimum Inhibitory Concentration (MIC)

Lowest concentration of drug that prevents growth of the pathogen

Minimum Lethal Concentration (MLC)

Lowest concentration of drug that kills the pathogen

Kirby-Bauer Method

Standardized method for disk diffusion test

Used to detect how susceptible a microbe is to an antimicrobial agent

Relates zone diameter with microbial resistance

Beta-Lactam Ring

Most important feature in penicillin

Essential for bioactivity

Acts by inhibiting transpeptidation, blocking cell wall formation

Penicillinases

Beta-lactamases that hydrolyze a bond in the beta-lactam ring, resulting in penicillin being rendered useless

Beta-Lactamases

Break the beta-lactam ring, making penicillin not effective

Cephalosporins

Inhibits transpeptidation reaction during peptidoglycan synthesis

Carbapenems

Broad-spectrum antibiotics that inhibit cell wall synthesis

Monobactams

Beta-lactam antibiotics, but their beta-lactam ring is not fused to another ring

Vancomycin

Glycopeptide antibiotic used as a last resort that inhibits cell wall synthesis

Binds to substrate (D-alanyl-D-alanine terminal sequence) instead of enzyme

Aminoglycoside Antibiotics

Large variation in structure, but all with a cyclohexane ring and amino sugars

Generally used in gram-negative bacteria

Bind to the 30S ribosomal subunit to interfere with mRNA reading and/or causing early termination of peptide synthesis, ultimately disrupting peptide elongation in translation

Tetracyclines

All have a four ring structure with a variety of side chains attached

Bacteriostatic and are broad spectrum

Target the 30S subunit of the ribosome, inhibiting protein synthesis

Macrolide Antibiotics

Bind to the 23S rRNA of 50S large ribosomal subunit to inhibit peptide chain elongation during protein synthesis

Oxazolidinones

Bind to the 50S ribosome and prevent formation of 70S initiation complex

Antimetabolites

Antagonize, or block, functioning of metabolic pathways

Broad spectrum

Sulfonamides

Prevents the production of folic acid, which in turn prevents the synthesis of DNA, RNA, proteins, and other important cellular constituents

Trimethoprim

Broad spectrum antibiotic that interferes with folic acid production

Often used to treat UTI

Binds to and competes with substrate for dihydrofolate reductase

Fluoroquinolones

Broad spectrum antibiotics that inhibit/disrupting DNA replication

Bind to bacterial DNA gyros and topoisomerase IV

Tamiflu

Used to treat the flu

Prevents the flu from being able to copy itself in the body, allowing for it to end days earlier than normal

Rifamycin

Inhibits bacterial transcription

Binds to the beta-subunit of RNA polymerase

Used to treat tuberculosis

Enzyme

Protein catalyst

Ribozyme

RNA catalyst