microbiology

spontaneous generation

• life can arise spontaneously from nonliving matter

• vital forces in nonliving matter can lead to a new life

• living cells can arise from nonliving matter under favorable conditions

biogenesis

• life can arise as a result of microorganisms present in nonliving matter

• microorganisms present in nonliving matter can lead to new microorganisms

• living cells can arise only from preexisting living cells

Louis Pasteur conducted an experiment to disprove the theory of spontaneous generation. match each component in the experiment with its purpose in this experiment

beef broth: provided a nutritious environment to support microbial growth

Bunsen burner (flame): provided heath that destroyed microorganisms already present in the beef broth

flask with S-shaped neck: provided the physical conditions for trapping airborne contaminants and preventing microorganism from entering the flask

air: provided a source of potential external microbial contaminants

Microbes

• produce vitamins in the intestines

• generate oxygen through photosynthesis

• play a role in breaking down waste and decomposing dead organisms

• only a small percentage produce diseases

• gene expression in bacteria is very similar to gene expressionn in humans, which facilitates the use of bacteria in recomninat biotechnology and gene therapy

what was the essential findings for Edward Jenners vaccination process?

exposure to a milder diseases form may produce immunity

equal to 1 nm

• 0.1 cm

• 1,000,000 nm

• 0.001 m

• 1,000,000,000 pm

Microscopes

darkfield microscope- uses visible light

fluorescence microscope- uses light produced by fluorophores

confocal microscope- produces a three-dimensional image

scanning tunneling microscope- allows visitation of atoms

scanning electron microscope- produces a three- dimensional image

dyes

• methylene blue- simple stain

• crystal violet- simple stain

• nigrosin- negative stain

• acidic dye- capsule stain

• Iodine- mordant

• alcohol-acetone- decolorizer

• carbolfuchsin- basic dye

in microscopy, the term resolution

refers to the ability to distinguish fine structure and detail in a specimen

• the ability to distinguish fine details and differentiate between two very close objects

Protozoan motility structures include

cilia, flagella, and pseudopods

Associated with viruses

• nucleic acid

• protein coat

• envelope

• chemical reactions

Kochs postulates

determination of the cause of a new emerging disease by scientists studying disease transmission

which theory is based on the observations of Hooke and van Leeuwenhoek, documenting the existence of microscopic cells

the cell theory, statin that all living things are composed of cells

Biofilms

• in pipes can block the flow of water

• in your body protect mucous membranes from harmful microbes

• on medical devices cause infections

• on rocks provide food for animal life

• not sensitive to antibiotics

what contributes to the rising incidence of antibiotics resistance?

random mutations, overuse and misuse of specific drugs

contribute to the threat of emerging infectious diseases (EID)

• spread of known diseases to new geographic regions or populations by modern transportation

• evolutionary changes to existing organisms through genetic changes

• increased human exposure to new, unusual infectious agents in areas that are undergoing ecological changes, such as deforestation and construction

which microscope achieves the highest magnification and greatest resolution

electron microscope

which microscope is most useful for visualizing a biofilm?

scanning acoustic microscope

what microscope takes advantage of differences in the refractive indexes of cell structures

phase-contrast microscope

the resolution of a microscope can be improved by changing the

wavelength of light

bacteria

• have cell walls that contain peptidoglycan

• derive nutrition from organic or inorganic sources or conduct photosynthesis

archaea

• found in extreme environments

• not typically associated with human disease

fungi

• eukaryotic

• can be unicellular or multicellular

viruses

• cannot reproduce outside a host cell

• can be seen only with an electron microscope

one of the first set of experiments to refute spontaneous generation was done by Francesco Redi

the results of his experiment demonstrated that living organisms are derived from other living organisms

limitations of antibiotics

• treatment with antibiotics can lead to the emergence of resistance strains

• antibiotics may be toxic

• not effective in treating viral infections

Prokaryotic cells

• lack membrane-enclosed organelles

• their DNA is not enclosed within a membrane

• they reproduce by binary fission

• typically have a circular chromosome

• peptidoglycan cantaining cell wall

• 70S ribosomes

what makes phospholipid membranes good at keeping some molecules out, and allowing others to freely pass?

they have both hydrophilic and hydrophobic regions

Integral proteins

transport function

how does water enter and exit the cell?

by simple diffusion or by use of an integral transport protein

Glycoprotein

is a type of peripheral protein above that can be used as a receptor or in enzymatic functions

which structure protects bacteria form being phagocytized

capsule

Gram-positive cell walls

• maintains the shape of the cell

• contains teichoic acids

• sensitive to lysozyme

• sensitive to penicillin

Hydrophobic molecules move across a membrane

by passive transport directly across the membrane

what is a hallmark of passive transport across cell membranes

is occurs along an electrochemical gradients, and may involve the use of transport proteins

A positively charged sodium ion

would require the use of integral protein channels to pass through a cell membrane

why is no energy required in passive transport?

the concentration gradient drives the movement

once equilibrium is reached

molecules move, but there is no net movement in a particular direction

what would not move freely across the cytoplasmic membrane

positively charged hydrogen ions

why is ATP necessary for active transport

ATP provides energy to transfer material against its concentration gradient

which type of active transport protein moves two molecules into the cell at the same time

symport

which transport protein employs transporters that move molecules only in one direction

uniport and symport

which type of active transport protein uses one protein to pump two different molecules

antiport and symport

Functions of the glycocalyx

• increased virulence

• biofilm formation

• source of nutrition

• protection against dehydration

Fimbriae and pili differ in that

pili are used for transfer of DNA and motility

Gram-negative bacteria

the thin layer of peptidoglycan is surrounded by outer membrane made of phospholipids, lipopolysaccharides, and proteins

the difference between simple diffusion and facilitated diffusion is that facilitated diffusion

requires transporter proteins

where are phospholipids most likely found in a eukaryotic cell

the plasma membrane and organelles

DNA found in most bacterial cells

is circular in structure

in a bacterial ribosomes, a small 30S subunit and a large 50S subunit come together to produce the functional 70S ribosome. why isn’t it an 80S ribosome?

S stands for Svedberg units, which indicates the relative rate of sedimentation due to size, weight, and shape of a particle. the numbers aren’t strictly additive

how is osmosis different from simple diffusion

water movement is driven by the concentration of solutes rather than its own concentration

Nonspecific permeases

allow a variety of molecules to cross the cytoplasmic membrane

what will happen to a cell that is placed in a solution containing a high concentration of sugar, a molecule that cannot pass across the cell membrane?

the cell will lose its interior water, causing it to shrivel up and possibly die

How is simple diffusion different from other types of passive transport?

simple diffusion does not require a permease

Eukaryotic cells

• mitochondria; lysosomes; Golgi apparatus; endoplasmic reticulum

• 80s ribosomes

• cellulose or chitin-containing cell wall

• linear chromosomes enclosed within a nuclear envelope

• flagella that wave, composed of microtubules

Structures found in all bacterial cells

• cytoplasm

• ribosomes

• plasma membrane

• nucleoid

Indicate the bacterial structures that are likely to be antigens, to which host antibodies bind, marking the invader for phagocytosis

• capsule

• fimbriae

• flagella

• cell wall

identify antibacterial strategies that would likely be selectively toxic for bacteria

• inhibition of peptidoglycan synthesis

• inhibition of fimbriae synthesis

• interfering with translation at 70S ribosomes

Bacterial growth curve

(1) lag phase:bacteria are metabolically very active, but the numbers are not increasing

(2) log phase: period of most rapid growth. number of bacteria is increasing exponentially

(3) stationary phase: population growth has halted. number of new cells formed balances the number of cells dying

(4) death phase: rate of the cell death exceeds the rate at which new cells are being formed. numbers of cells decline exponentially

when bacteria are inoculated into a new sterile nutrient broth, their numbers don’t begin to increase immediately. instead, there is a lag phase that may last several hours/days. why don’t bacterial numbers increase immediately?

the bacteria must adjust to the nutrients content in the new medium, synthesizing necessary amino acids, growth factors, and enzymes

describe what is happening to bacterial cultures during stationary phase

• harmful waste products may be accumulating

• the number of cells that are dying is balanced by the number of new cells that are being formed

• the cells are likely running out of nutrients

Chemostats

provide a continues source of fresh nutrients and remove wastes and dead bacterial cells

which method would be most appropriate for gathering data to plot a bacterial growth curve throughout the four phases?

plate count will provide the number of living cells

what enables the copied chromosomes to separate during binary fission?

the chromosomes are attached to different parts of cell membrane, which elongates and thus separates the chromosomes

how long does it take for the daughter cells to initiate/ start the next round of replication

no time is required- they are ready to divide immediately after DNA replication and separation of the daughter cells is complete if conditions are right

Steps of bacterial replication

1) chromosome replication

2) cell elongation

3) septum formation

4) separation of daughter cells

what would happen if the septum did not form during binary fission?

the parent cell would now have two copies of the chromosomes

if cells are grown in media containing amino acids labeled with radioactive nitrogen (^15N), most of the radioactivity will be found in the cells

DNA and proteins

Fungi grow best at pH

5

Aerotolerant anaerobe

an organism that does not use oxygen but tolerates it

which enzyme catalyzes the following reaction? 2H2O2—→2H2O + O2

catalase

which microbes are most likely to cause human disease, based on their temperature requirements?

mesophiles

the source of nutrients in nutrient agar is

peptone and beef extract

which process is best for the short-term storage of bacterial cultures?

refrigeration

generation time

the length of time needed for a cell to divide

which is NOT a direct method to measure microbial growth?

metabolic activity

which enzyme catalyzes the reaction: O2- + O2- +2H+—→ H2O2 + O2

superoxide dismutase

culture medium necessary for growing an obligate anaerobe, such as Clostridium tetani

receding media are complex media containing chemicals, such as thioglycolate, that combine with oxygen, creating an anaerobic environment

fecal coliforms in Lake of the Ozarks

• fecal coliform will likely contain enzymes to counteract toxic oxygen forms

• need to acquire trace elements for growth in the lake environment

• the lake environment will support the growth of facultative anaerobes

which of the following event occurs during transcription?

a molecule of RNA is formed based on the sequence of nucleotides in DNA

which of the following is correct statement about mRNA

mRNA moves from the nucleus to the cytoplasm following RNA processing

the site of translation is

ribosomes in the cell cytoplasm

what does not play a role in translation

DNA

which of the following options is a signature symptom of necrotizing fasciitis

loss of tissues around a wound

which of the following DNA sequence best represents a mutation of this sequence: 5’- TACGTAGCA - 3’

DNA: 5’- TACCTAGCA - 3’

what are the two steps A. baumannii uses to produce proteins from DNA

transcription and translation

which is NOT an example of horizontal gene transfer

a bacterium passes a mutates gene to its offspring via binary fission

a bacterial stain undergoes a chromosomal mutation that converts one of its genes to a resistance gene. later, you discover that some members of this strain now carry the gene on a plasmid. which of the following do you think accomplished this transfer?

a transposase

• are small segments of DNA that can “jump” from one DNA molecule to another using the enzyme transposase

A. baumannii became resistant to tetracycline by acquiring a R plasmid. which of the following best describes how A. baumannii obtained this R plasmid

horizontal gene transfer

what characteristic of DNA allows two connected DNA polymerases to synthesize both the leading and lagging strands?

DNA is flexible

what is the function of the connector proteins?

they link the leading strand DNA polymerase and the lagging strand DNA polymerase together

which DNA strand is synthesized continuously?

leading strand

which of the terms are associated with Okazaki fragments

lagging strand, DNA ligase, and discontinuous

why is the DNA synthesis of the lagging strand considered discontinuous?

the synthesis is moving in the opposite direction from the replication fork

An enzyme that copies DNA to make a molecule of RNA is

RNA polymerase

Which of the following is a DNA strand complementary to CGA ATC AGC?

GCT TAG TCG

Replication

DNA—> 2 DNA (copying one DNA molecule to make two identical DNA molecules)

Gene expression

DNA—>mRNA—> protein

• transcription

• translation

Recombination

• transformation

• transduction

• conjugation

DNA replication

• DNA helices separates the DNA strands, creating a replication fork

• DNA replication can copy plasmids, which can be transferred among bacterial cells of the same generation

• DNA replication is semiconservative

• DNA replication occurs prior to mitosis and prior to binary fission

• Topoisomerase and DNA gyrase remove supercoiling ahead of the replication fork

• the major replication enzyme is DNA polymerase

• DNA replication provides an exact copy of DNA for daughter cells (next generation)