Microbiology 319 Chapter 9

Exam #2: Lectures 14-16

Most bacteria reproduce by…

Binary fission

During bacterial cell growth, the cell primarily…

Increases in size and produces proteins

DNA replication in bacteria begins at the…

Origin of replication

Which step involves movement of DNA to opposite sides of the cell?

Chromosome segregation

The Z-ring is formed by which protein?

FtsZ

The septum is…

The inward growth of membrane and wall

What happens during cell separation?

Parent splits into two identical cells

Exponential growth means…

Cells double at a constant rate

The formula for bacterial growth is…

N_n = N₀ × 2ⁿ

Which phase shows the fastest growth?

Log growth

In the lag phase, bacteria…

Prepare for division

In the stationary phase…

Growth equals death

Budding

Cell size is unequal

Multiple Fission

Makes more daughter cells at once

Fragmentation

Filamentous bacteria

Intracellular Offspring

Develop internally

A chemostat is…

A continuous culture system

In a chemostat, cell number remains constant because…

Input equals output

Continuous Culture

Fresh medium is continually added and an equal amount is taken off, so bacteria can be kept in exponential phase for long periods

Growth rate in a chemostat is controlled by…

Limiting nutrient

Biofilms are…

Surface attached microbial communities

EPS in biofilms act as…

Glue-like matrix

Channels in biofilms allow…

Movement of nutrients and waste

Which counting method counts both live and dead cells?

Direct count

Plate count measures…

Only living cells

A spectrophotometer measures…

Turbidity

Which is a physical growth requirement?

Temperature

Which is a chemical growth requirement?

Carbon

Facultative Anaerobes

Can grow with or without oxygen

Microaerophiles

Require low oxygen

Strict Aerobe

Growth only in oxygen

Strict Anaerobe

Growth only without oxygen

Aerobic Respiration

The use of O₂ as the terminal electron acceptor

Aerotolerant Anaerobes

Use only fermentation to provide energy

The formula N_n = N₀ × 2ⁿ is used to calculate…

Number of cells at a given generation

In the equation N_n = N₀ × 2ⁿ, what does “n” represent?

Number of generations

A bacterial culture’s growth curve is plotted as…

Logarithm of number of live cells vs. time

Which device allows continuous addition of nutrients and removal of wastes to maintain bacterial growth?

Chemostat

The Petroff-Hausser chamber is used for…

Direct cell counting

A disadvantage of direct cell counting using a Petroff-Hausser chamber is…

Cannot differentiate live from dead cells

For plate counts, a reliable number of colonies is typically…

30-300

Advantages of plate counting include…

Rapid counting and direct visualization

In the SYTO 9 / Propidium Iodide method…

SYTO 9 stains live cells green, PI stains dead cells red

One limitation of using SYTO 9 / PI staining is…

Requires fluorescence microscopy

Which method measures cell density by light scattering?

Spectrophotometer

A Coulter counter detects bacterial cells by…

Current flow deflection

Which of the following is a physical requirement for bacterial growth

pH

Psychrophilic bacteria grow optimally at…

0-15 C

An organism that grows best at 37 C in high salt and alkaline conditions is likely not a…

Psychrophile

An organism that grows at 10 C could be…

Psychrophile & Psychotroph

Most bacteria cannot grow in oxygen because…

They lack enzymes to detoxify reactive oxygen species

Microaerophiles grow best in…

Low oxygen concentrations

The enzyme that converts superoxide radicals (O₂^-) to H₂O₂ is…

Superoxide dismutase

Hydrogen peroxide is converted into water and oxygen by…

Catalase

Oxygen can damage cells primarily by…

Oxidizing biomolecules

Which type of medium contains inhibitors to restrict growth to certain bacteria?

Selective

Differential Media

Enable different species to be distinguished from each other

Enrichment Media

Encourage the growth of a specific organism

Which medium allows differentiate based on hemolysis?

Blood agar

MacConkey agar differentiates bacteria based on…

Lactose fermentation

Mannitol Salt Agar (MSA) is…

Selective for high salt tolerance and differential for mannitol fermentation; selective for staphylococcus

Most microbes in the world are…

Anaerobic

Organisms that rely solely on fermentation but tolerate oxygen are called…

Aerotolerant anaerobes

Defined media differs from complex media because…

All components and ratios are known

Agar

A solidifying agent not metabolized by most microbes

Fanny Angelina Hesse is credited with…

Introducing agar into laboratory research

Selective Media

Limits growth to certain organisms

Beta-hemolysis is characterized by…

Complete lysis, clear zone

Deep freezing of bacterial cultures occurs at…

-50 to -95 C

Lyophilization (Freeze-drying) involves…

Freezing and dehydrating in a vacuum