BIOL2730 Pathogenic Microbiology Sassanella Chapter 04

Binary fission

Is the asexual process of reproduction in which one cell divides into two daughter cells

Generation time

The time it takes for a population to double in number

Biofilm

Is any group of microorganisms in which cells stick to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance (EPS). Wikipedia

Extracellular polymeric substances (EPS)

Are high-molecular weight compounds secreted by microorganisms into their environment. Wikipedia

Aseptic technique

Refers to a procedure that is performed under sterile conditions. This includes medical and laboratory techniques, such as with cultures. It includes techniques like flame sterilization. Wikipedia.

Colony

Individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defense or the ability to attack bigger prey. Wikipedia.

Agar

A gelatinous material derived from algae, specifically used as a culture medium of bacteria and other cells for diagnostic or laboratory experiments purposes.

Petri dish

A Petri dish (sometimes spelled "Petrie dish" and alternatively known as a Petri plate or cell-culture dish), named after the German bacteriologist Julius Richard Petri, is a shallow cylindrical glass or plastic lidded dish that biologists use to culture cells - such as bacteria - or small mosses.

Exponential or log-phase growth

A growth in which the rate is proportional to the increasing number or size in an exponential (rather than arithmetical) or logarithmic progression . Biologyonline.org.

Primary and secondary metabolite production

Primary metabolites are synthesized during the period of active multiplication (examples are ethanol or commercial amino acid suppliments) and secondary metabolites being to be synthesized in late log phase ( examples include most antibiotics).

Psychrophile

Are extremophilic bacteria or archaea which are cold‐loving, having an optimal temperature for growth at about 15°C or lower, a maximal temperature for growth at about 20°C and a minimal temperature for growth at 0°C or lower. Encyclopedia of Life Sciences

Mesophile

Is an organism that grows best in moderate temperature, neither too hot nor too cold, typically between 20 and 45 °C (68 and 113 °F). The term is mainly applied to microorganisms. Wikipedia

Thermophile

Is an organism — a type of extremophile — that thrives at relatively high temperatures, between 41 and 122 °C (106 and 252 °F).[ Many thermophiles are archaea. Thermophilic eubacteria are suggested to have been among the earliest bacteria. Wikipedia.

Obligate aerobe

Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest.

Facultative anaerobe

A facultative anaerobe is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation or anaerobic respiration if oxygen is absent.

Obligate anaerobe

Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest.

Neutrophile (ph)

A neutrophile is an organism that thrives in neutral pH environments.

Acidophile (ph)

Acidophiles or acidophilic organisms are those that thrive under highly acidic conditions (usually at pH 2.0 or below). These organisms can be found in different branches of the tree of life, including Archaea, Bacteria, and Eukaryotes.

Alkaliphile (ph)

They are a class of extremophilic microbes capable of survival in alkaline (pH roughly 8.5-11) environments, growing optimally around a pH of 10.

Halotolerant

Able to tolerate a high concentration of salt in its environment.

Halophile

Organisms that thrive in high salt concentrations. They are a type of extremophile organism. The name comes from the Greek word for "salt-loving".

Complex media

Contains a variety of ingredients such as meat juices and digested proteins, and sometimes additional mixed nutrients.

Chemically defined media

They are composed of exact amounts of pure chemicals.

Selective media

Inhibit the growth of certain species, making it easier to isolate the one being sought.

Differential media

Tests for a biochemical capability and contains chemicals that certain microbes change in a recognizable way (usually by changing color).

Fastidious

They have complicated growth requirements.

Why do you use measure generation time in log-phase cultures?

The exponential phase is medically important because bacteria are most sensitive to antimicrobial medications at this stage. Many of these medications target processes primarily active when bacteria are multiplying generation time is measured in log phase because some of the molecules made by the growing cells are valuable, by using generation time you can calculate when the cells have reached their valuable state.

Be able to provide an example of a biofilm from the slides.

Dental plaque

How could biofilms affect antibiotic resistance?

The biofilm matrix can act as a barrier to delay the diffusion of antibiotics into biofilms because antibiotics may either react chemically with biofilm matrix components or attach to anionic polysaccharides. If the time required for an antibiotic to penetrate biofilms is longer than the duration of antibiotic treatment,

the slower penetration will explain the antibiotic resistance. Medscape.com

Why would you do a streak plate?

In microbiology, streaking is a technique used to isolate a pure strain from a single species of microorganism, often bacteria. Samples can then be taken from the resulting colonies and a microbiological culture can be grown on a new plate so that the organism can be identified, studied, or tested. Wikipedia.

Name the five phases of a growth curve

Lag phase, exponential or log phase, stationary phase, death phase, and phase of prolonged decline.

Which two stages are most important in the pharmaceutical industry?

Log or exponential phase (primary, supplements), and stationary phase (secondary, antiobiotics)

Give two examples of bacterial products (from lecture or slides) that bacteria can produce as a result of primary or secondary metabolite production

Ethanol or commercial amino acids.

What are the two most relevant chemicals in medically related situations to change osmolarity (make solutions hypertonic or hypotonic)?

Water and salt.

Which pH conditions are human pathogenic bacteria likely to prefer?

PH5 - PH8

If we assume that there are plenty of the essential metals (phosphorus, potassium, magnesium, calcium, iron, cobalt, zinc, copper, molybdenum, and manganese) in the media, name the four critical non-metallic elements that are essential for bacterial growth.

Carbon, nitrogen, hydrogen, and sulfur.

Name three types of sources of energy from bacteria.

Sunlight, organic matter, and inorganic matter.

Name one type of media that is selective and one that is differential, and why (from the slides).

Blood Agar and MacConkey Agar. Blood Agar is a complex medium that is differential for beta and alpha hemolysis. MacConkey Agar is a complex medium that is differential for lactose fermentation and selective for Gram-negative rods.

You use a counting chamber (with a microscope) or a Coulter counter for doing what measurement?

To determine the number of microbial cells per ml.

Describe how to do a 1:10 serial dilution.

By adding 1 ml of culture to 9 ml of diluent results is a 1:10 dilution.

What is one way to concentrate bacteria that occur in large volumes of liquid (like urine)?

Membrane filtration

Which common laboratory device makes determining the concentration of substances or cells in solution quick and easy?

Spectrophotometer

When doing a serial dilution for plating bacteria, why would you want to dilute them down until you get 30-300 CFUs (colony forming units or cells) per plate? (check your text for this one) . Would this be the best way to gather the data to determine a growth curve (the first experiment) or when a culture is in log-phase growth (subsequently)?

Plates with more than 300 CFU are very difficult to count. Plates with less than 30 CFU are not statistically reliable. If you can see turbidity in a broth culture you have millions more bacteria than you need. So generally, this allows you to see the individual colonies. When a culture is in log-phase.