UTA Microbiology Exam 3

4 Basic Steps of binary fission

1. Growth of cell size

2. Replication of DNA

3. Division of cytoplasm

4. Septum formation & cell division

Z Ring Assembly

FtsZ assembles Z ring to form divisome

Generation Time

time it takes to double the population

Lag Phase

Cells adjust to culture medium; no change in population

What factors determine the duration of the lag phase?

Genetic makeup, media composition, initial inoculum size

During which phase of the growth curve is it most appropriate for the use of antibiotics?

Log phase

Following the death phase of the growth curve, ____ cells are considered the surviving cells & are considered clinically important due to their association with chronic infections, such as Tuberculosis.

Persisters

Log Phase

Binary fission occurs; cell replication > cell death

Stationary Phase

Resources become depleted; cell respiration=cell death

Death Phase

Endospores can form; cell replication < cell death

Close System Cultures

Have finite resources

Open System Cultures

-Nutrients and air are replenished

-Dead cells and waste are removed

-Beneficial for industrial microbiology

Microscopic Cell Count

Cells are counted under a microscope using a laser etched slide

In using the direct microscopic cell count method, you will be able to distinguish between live vs dead cells.

False

Fluorescence Staining

Cells are counted under a microscope or flow cytometer

In fluorescent staining, the end product results in live cells staining ___________?

Green

In fluorescent staining, the end product results in dead cells staining ___________?

Red

Coulter counting

Detects electrical resistance change due to cell density

Viable Cell Counts

Samples are diluted and grown on solid media

What type of cells are counted when using the viable plate count method?

Living

Countable Range

30-300 CFU/ml

Optical Density

-Measured with spectrophotometer

-Light is passed thru culture and measured on other side

Which method of measuring growth is considered an indirect approach?

Optical density

Which method of measuring growth can be used on living or dead cells?

Fluorescent stain

How is the pour plate technique set up?

The sample is mixed with a warm agar ranging from 45-50 C, poured onto sterile plated and swirled to mix

How is the spread plate technique set up?

The sample is poured onto a solid medium and spread using a L spreader

What cell counting method is used for counting colonies from drinking water?

Membrane filtration

What method of measuring growth is used in food/water testing?

MPN (most probable number)

Steps of Biofilm Formation

1. Attachment of planktonic cells

2. Cells become sessile

3. Growth & Division on substrate

4. Production of extracellular polymeric substance

5. Attachment of secondary colonizers & dispersion

Quorum Sensing

Cell to cell communication regarding cell density

What is the term that refers to the small molecules that allow microbes to detect cell density in a biofilm?

Autoinducers

What is EPS composed of?

Hydrated polysaccharide gel, other macros & channels

How is EPS used in a biofilm?

It is secreted by the organisms

When using the optical density method, when the bacteria increases, turbidity________?

Increases

Which pattern of growth is often observed in actinomycetes and anaerobic, gram-positive bacteria?

Fragmentation

Where is biofilm formation typically found?

Liquid environments; rivers, pipelines, oral cavities

When is MPN used?

When counts are lower than 30 CFU/ml

What two classes make up signaling molecules?

1. N-actuated homoserine lactones

2. Various short peptides

Where can the signaling molecule, N-acylated homoserine lactones, be found?

Gram negative bacteria

Where can signaling molecules, such as a variety of short peptides, be found?

Gram positive bacteria

What is considered a "good" type of biofilm found in the human body?

Normal biota in the lungs

What is considered a "bad" type of biofilm found in the human body?

Plaque on teeth

Obligate Aerobes

must have oxygen to survive

Obligate Anaerobes

will die in the presence of oxygen

Facultative Anaerobes

Can live without oxygen, but prefer it

Aerotolerant Anaerobes

Tolerant of oxygen, but don't use it

Microaerophiles

require 1-10% oxygen levels to function

What does FTM stand for?

Fluid Thioglycollate Medium

What does FTM test for?

The oxygen requirement of a certain bacteria, with the use of agar tube

How is aero tolerance of a bacteria determined?

Growth location in test tube

What bacterial species consists of obligate anaerobes?

Bacteroides

What bacterial species consists of obligate aerobes?

Micrococcus luteus

What bacterial species consists of facultative anaerobes?

Staphylococcus

What bacterial species is considered aero tolerant?

Lactobacillus

What species consists of microaerophiles?

Campylobacter

What are the main factors that affect growth?

Oxygen level, pH, temperature, osmotic pressure, barometric pressure

What macro is most affected by pH?

Proteins

What type of microbe is most adapted to a pH that is acidic?

Fermenters

Which groups of bacteria are considered neutrophiles?

E.coli, staphylococci, salmonella

Which groups of bacteria are considered acidophiles?

Fermenting bacteria; proteins/phospholipids

What group of bacteria is considered alkaliphiles?

Vibrio cholera

Neutrophiles

Optimal pH around 7

Acidophiles

Optimal pH < 5.5

Alkaphiles

Optimal pH is 8-10.5

What temperature do mesophiles require to grow?

Prefer room temp. (20-40C)

What temperature do Psychotrophs require for growth?

Prefer cooler temp. (4-20C)

What temperature do psychrophiles require for growth?

permanently cold temps. (<0C)

What temperature do thermophiles require for growth?

Prefer hot temp. (50-80C)

What temperature do Hyperthermophiles require for growth?

Extreme hot temp. (80-110C)

What are psychotrophs responsible for?

Refrigerated food spoilage

Where are mesophiles found?

Human body

Where can psychrophiles be found?

cold waters, bottom of the ocean

Where can thermophiles be found?

Compost piles, hot springs, soils

Where can hyperthermophiles be found?

Hyperthermal ocean vents

Halophiles

Salt/solute lovers; found in oceans

Halotolerant

Tolerate high salt, but don't need it; found in salt marshes where high solutes aren't present all the time

What bacterial species is considered Halotolerant and is an important cause for foodborne illness?

Staphylococci

Where are Barophiles found?

Bottom of the ocean

What type of microbes depend on light for growth?

Photoautotrophs, photoheterotrophs

What type of bacteria is considered photoautotrophs?

Cyanobacteria, green sulfur

What type of bacteria is considered photoheterotrophs?

Purple nonsulfurs

What is the difference between selective media and differential media?

Selective SELECTS the organism for growth while inhibiting all others

Differential causes all present organisms to grow, but is able to differentiate fermenters vs Non via color change

Sterilization

Removal/killing of all mircrobes

Disinfection

Inactivation of microbes, removal of some on fomite

Antisepsis

Acts on microbes, but not tissue; safe on skin

Degerming

Reduces microbial load on living tissue with use of mechanical process

Sanitization

Decreasing microbial load on fomite with use of heat/chemicals

Antiseptic technique is used to prevent contamination of a sterile environment.

True

What are the most prominent methods of sterilization used?

Heat, pressure, filtration, chemical

examples of disinfectants

Vinegar, bleach

examples of antiseptics

alcohol, hydrogen peroxide

Which biosafety level poses as a moderate risk and requires restrictive access?

BSL-2

Which biosafety level can cause potential lethal infections by inhalation and require directional air flow?

BSL-3

What indigenous pathogens can be found in a BSL-3?

TB, anthrax, West Nile, HIV

What indigenous pathogens can be found in a BSL-4?

Ebola, Marburg, smallpox

What biosafety level is appropriate for Salmonella?

BSL-2

Critical

Must be sterile; items contact sterile tissue (in body)

Semicritical

Do not require high level sterilization; items might contact non-sterile tissue, no penetration

Noncritical

Do not require sterilization; items contact but do not penetrate

What medical tools can be considered critical?

surgical instruments, cathedar, IV