Microbiology Exam 2

____ inhibition, typical of anabolic (biosynthetic) pathways, allows a cell to adapt to short-term fluctuations in the supply of a needed substance.

Feedback

_____ ; pili (singular, pilus). •Short, thin, hairlike, protein appendages (up to 1,000/cell). Can mediate attachment to surfaces, motility, DNA uptake.

Fimbriae

External structures extend beyond the cell envelope in bacteria; Function in protection, attachment to surfaces, horizontal gene transfer, cell movement. •Pili and fimbriae. •_____.

Flagella

In 1928 _____ carries out experiments that identify a transforming substance using non-pathogenic and pathogenic strains of pneumonococcus.

Frederick Griffith

The best studied bacterial cytoskeletal proteins are ____, MreB, and CreS. Here they are shown in photos of cells viewed by fluorescence microscopy. (Top) FtsZ-green fluorescent (GFP) fusion protein in a chain of Bacillus subtilis cells arranged end-to-end. (Center) The MreB-like GFP cytoskeletal protein of B. subtilis. With this method, Mbl seems to form helices. (Bottom) CreS (also known as crescentin) of Caulobacter crescentus appears red along the inner curve of the cell. The DNA in the cells, along the outer curve of the cell, was stained blue with DAPI.

FtsZ

______ Motility is when multiple flagella form axial fibril which winds around the cell. -Flagella remain in periplasmic space inside outer sheath. -Corkscrew shape exhibits flexing and spinning movements.

Spirochete

Chemotaxi movement: (Left) Random movement of a bacterium in the ____ of a concentration gradient. Tumbling frequency is fairly constant. (Right) Movement in an attractant gradient. Tumbling frequency is reduced when the bacterium is moving up the gradient. Therefore runs in the direction of increasing attractant are longer.

absence

When Meselson and Stahl developed this technique in the mid-1950s, it represented the first method to separate molecules of similar size but of different _____. Meselson and Stahl employed their method to determine how DNA replicates, and it became known as the Meselson-Stahl experiment

density

The differences between cell types are due to ___gene expression, the expression of different genes by cells with the same genome.

differential

Gene expression must be controlled on a long-term basis during cellular ____, the divergence in form and function as cells in a multicellular organism specialize.

differentiation

In the ___ model, Each strand of both "daughter" molecules contains a mixture of old and newly synthesized DNA. This model attempts to solve the problem of unwinding the two strands of the double helix by a mechanism that breaks the DNA backbone every 10 nucleotides or so, untwists the molecule, and attaches the old strand to the end of the newly synthesized one. This would synthesize the DNA in short pieces alternating from one strand to the other.

dispersive

Cells can adjust the activity of ____ already present. This may happen by feedback inhibition, in which the activity of the first enzyme in a pathway is inhibited by the pathway's end product.

enzymes

In bacteria cytoskeleton, functions are similar as in ______. •Participate in cell division. •Localize proteins. •Determine cell shape.

eukaryotes

The endospore structure has: -Spore surrounded by thin covering called _____. =Thick layers of protein form the spore coat. -Cortex, beneath the coat, thick peptidoglycan. -Core has nucleoid and ribosomes.

exosporium

Cells can vary the number of specific enzyme molecules they make by regulating gene ____. Genes of the bacterial genome may be switched on or off by changes in the metabolic status of the cell.

expression

_______ are threadlike, locomotor appendages extending outward from plasma membrane and cell wall. Functions. •Motility and swarming behavior. •Attachment to surfaces. •May be virulence factors..

flagella

Sporolation cycle: Cell division is at the top of the cycle. I.Axial filament formation. II.Septum formation and forespore development. III.Engulfment of _____. IV.Cortex formation. V.Coat synthesis. VI.Completion of coat synthesis, increase in refractility and heat resistance. VII.Lysis of sporangium, spore liberation.

forespore

Classification of plasmids via mode of existence, spread, and ____.

function

____ motility is: •Smooth movements.

gliding

MreB—many rods. Maintains shape by positioning _____ synthesis machinery

peptidoglycan

Intracytoplasimic memebranes, involve plasma membrane infoldings. •Observed in many _____ bacteria. •Observed in many bacteria with high respiratory activity.

photosynthetic

Sex ____ (singular, pilus). •Longer, thicker, less numerous •(1 to 10 per cell). •Genes for formation on plasmids. •Required for conjugation.

pili

_____, are extrachromosomal DNA. •Usually small, closed circular DNA molecules which are highly coiled and Exist and replicate independently of chromosome. •Episomes—may integrate into chromosome. •Inherited during cell division.

plasmids

Beadle and Tatum's idea has been restated as the one gene-one ______hypothesis. Some genes code for RNA molecules that play important roles in cells although they are never translated into protein.

polypeptide

As the DNA is synthesized, nucleotides are added on to the growing chain by the DNA polymerase. However, on occasion a dideoxynucleotide is incorporated into the chain in place of a normal nucleotide, which results in a chain-_____ event.

terminating

Bacteria often respond to environmental change by regulating _____.

transcription

Chromatin configuration in turn influences ____.

transcription

In all organisms, the expression of specific genes is most commonly regulated at _____, often in response to signals coming from outside the cell. For this reason, the term gene expression is often equated with transcription.

transcription

The discovery that DNA borne on chromosomes is the hereditary material began with research by Frederick Griffith in 1928. He studied Streptococcus pneumoniae, a bacterium that causes pneumonia in mammals. One strain, the R (rough) strain, was harmless. The other strain, the S (smooth) strain, was pathogenic. Griffith mixed heat-killed S strain with live R strain bacteria and injected this into a mouse. The mouse died, and he recovered the pathogenic strain from the mouse's blood. Griffith called this phenomenon ______, (a phenomenon now defined as a change in genotype and phenotype due to the assimilation of foreign DNA by a cell).

transformation

A bacterium in a tryptophan-rich environment that stops producing ____ conserves its resources. Metabolic control occurs on two levels.

tryptophan

_____ motility is: •Pili at ends of cell. •Short, intermittent, jerky motions. •Cells are in contact with each other and surface.

twitching

Like ___ organisms, the tens of thousands of genes in the cells of multicellular eukaryotes are continuously turned on and off in response to signals from their internal and external environments.

unicellular

Highly specialized cells, such as nerves or muscles, express only a tiny fraction of their genes. Although all the cells in an organism contain an identical genome, the subset of genes expressed in the cells of each type is ___.

unique

Formation of the _____ cell: 1. Activation. •Prepares endospores for germination. •Often results from treatments like heating. 2. Germination. •Environmental nutrients are detected. •Spore swelling and rupture of absorption of spore coat. •Increased metabolic activity. 3. Outgrowth. •Emergence of vegetative cell.

vegetative

The genomes of eukaryotes may contain tens of thousands of genes. For quite a few species, only a small amount of the DNA—____in humans—codes for protein. Of the remaining DNA, a very small fraction consists of genes for rRNA and tRNA.

1.5%

Bacterial ribosomal RNA has: •___ small subunit. -23S and 5S in large subunit

16S

The Dideoxy Chain-Termination Method for Sequencing DNA 2. Synthesis of each new strand starts at the ____' end of the primer and continues until a dideoxyribonucleotide is inserted, instead of the normal deoxyribonucleotide. The dideoxy nucleotide prevents further elongation of the strand. Eventually a set of labeled strands of various lengths is generated, with the color of the tag representing the last nucleotide in the sequence.

3

_____—one flagellum at each end of cell.

Amphitrichous

_____ —CO2 fixing bacteria. •Contain the enzyme *RubisCO for CO2 fixation.

Carboxysomes

_____, are movement toward a chemical attractant or away from a chemical repellent. Changing concentrations of chemical attractants and chemical repellents bind chemoreceptors of chemosensingsystem

Chemotaxis

____ modifications affect the availability of genes for transcription.

Chromatin

________—material bounded by the plasmid membrane.

Cytoplasm

Finally in 1944, Oswald Avery, Maclyn McCarty, and Colin MacLeod working at the Rockefeller Institute in New York announced, albeit somewhat cautiously, that the transforming substance was _____ but Avery and his colleagues were clearly being very cautious in their conclusions, never stating that they was certain that DNA was the transforming agent. It is possible that his cautiousness with the matter contributed to the lack of attention it received.

DNA

In 1952 Alfred Hershey and Martha Chase demonstrate that the transforming principle in phage infection is ____.

DNA

____ gene expression is the expression of different genes by cells with the same genome. A typical human cell probably expresses about 20% of its genes at any given time.

Differential

Once the primer is attached to the DNA, the solution is divided into four tubes labeled "G", "A", "T" and "C". Then reagents are added to these samples as follows: "G" tube: all four dNTP's, dd____ and DNA polymerase "A" tube: all four dNTP's, ddATP and DNA polymerase "T" tube: all four dNTP' , ddTTP and DNA polymerase "C" tube: all four dNTP's, ddCTP and DNA polymerase

GTP

_____ are found in aquatic, photosynthetic bacteria and archaea. They provide buoyancy in gas vesicles.

Gas Vacuoles

Storage inclusions: Storage of nutrients, metabolic end products, energy, building blocks. _____ storage. Carbon storage . Phosphate—polyphosphate. Amino acids—cyanophycin granules. -poly-β-hydroxybutyrate (PHB).

Glycogen

_____—cluster of flagella at one or both ends

Lophotrichous

____ are found in aquatic bacteria. Magnetite particles for orientation in Earth's magnetic field. An interesting cytoskeletal protein MamK. •Helps form magnetosome chain.

Magnetosomes

_____, are not bound by membranes but compartments for specific functions. Carboxysomes—CO2 fixing bacteria. •Contain the enzyme *RubisCO for CO2 fixation.

Microcompartments

____ —one flagellum.

Monotrichous

Bacterial cytoplasmic structures include: -Cytoskelton -Intracytoplasmic membranes -Inclusions -Ribosomes -__________ -Plasmids

Nucleoid

In 1944 _____ et al. perform in vitro transformation experiments using highly purified DNA, which strongly suggest that this is the hereditary molecule.

Oswald Avery

_____—spread over entire surface of cell

Peritrichous

____—flagellum at end of cell.

Polar flagellum

________ is plasma membrane and everything within.

Protoplast

In Eukaryotes it had been Observed that the fact that cells double the amount of DNA in a cell prior to mitosis in Interphase of the __ phase and then distribute the DNA equally to each daughter cell provided some circumstantial evidence that DNA was the genetic material in eukaryotes.

S

Alfred Hershey and Martha Chase showed that DNA was the genetic material of the phage ___.

T2

______ Motility may involve Type IV pili and slime.

Twitching and Gliding

_____ consist of DNA (or sometimes RNA) enclosed by a protective coat of protein. To replicate, a virus infects a host cell and takes over the cell's metabolic machinery.

Viruses

DAPI, (pronounced as 'DAPPY') or 4′,6-diamidino-2-phenylindole, is a fluorescent stain that binds strongly to _____ rich regions in DNA. It is used extensively in fluorescence microscopy. As DAPI can pass through an intact cell membrane, it can be used to stain both live and fixed cells, though it passes through the membrane less efficiently in live cells and therefore provides a marker for membrane viability.

adenine-thymine

Homologs of all 3 eukaryotic cytoskeletal elements have been identified in ______ cytoskeleton. •Actin filaments. •Microtubules. •Intermediate filaments.

bacteria

______ flagella are thin, rigid protein structures that cannot be observed with bright-field microscope unless specially stained. Ultrastructure composed of three parts. •Filament extends from cell surface to the tip. •Basal body is series of rings that drive flagellar motor. •Hook links filament to basal body. •In the Gram-negative example (left) the L ring of the basal body is in the outer membrane of the cell and the P ring is in the peptidoglycan layer. The Gram-positive example (right) lacks the L ring and the P ring. In both examples, the basal body starts in the plasma membrane and extends out through the cell wall with the hook, and finally the filament of the flagellum.

bacterial

The ____ _____ is a complex, dormant structure formed by some bacteria. -Various locations within the cell. Resistant to numerous environmental conditions (including heat, radiation, chemicals, desiccation) due to: •Calcium (complexed with dipicolinic acid). •Small, acid-soluble, DNA-binding proteins (SASPs). •Dehydrated core. •Spore coat and exosporium protect.

bacterial endospore

Viruses that specifically attack bacteria are called _____ or just phages.

bacteriophages

Almost alone among the scientists of the time, Chargaff accepted the unusual Avery report and concluded that genetic differences among DNAs must be reflected in _____ differences among these substances. He was actually the first biochemist to reorganize his laboratory to test this hypothesis, which he went on to prove by 1949.

chemical

Bacterial _____ are located in the nucleoid, an area in the cytoplasm.

chromosomes

In the ____ model, The two parental strands reassociate after acting as templates for new strands, thus restoring the "parental "double helix.

conservitive

CreS—rare, maintains ____ shape.

curve

While some enzymes methylate the tails of histone proteins, other enzymes methylate certain bases in DNA itself. The DNA of most plants, animals, and fungi has methylated bases, usually ____

cytosine

Poly β-hydroxybutyrate is composed of β-hydroxybutyrate molecules joined by ester bonds between the carboxyl and hydroxyl groups of adjacent molecules. PHB inclusions are around 0.2 to 0.7 μm in diameter. They are seen as empty holes by electron microscopy because PHB is _____ and is dissolved by the solvents used to prepare specimens. PHB is enclosed by a shell composed of several different proteins, including the PHB-synthesizing enzyme and the PHB-degrading enzyme. Phospholipids are also found in the shell, however note that these phospholipids do not form a phospholipid bilayer.

hydrophobic

Hershey and Chase concluded that the injected DNA of the phage provides the genetic information that makes the ____ cells produce new viral DNA and proteins to assemble into new viruses.

infected

To determine the source of genetic material in the phage, Hershey and Chase designed an experiment in which they could label protein or DNA and then track which entered the E. coli cell during ____.

infection

Meselson and Stahl invented a specific type of density gradient centrifugation, called _______centrifugation that used a solution of cesium chloride to separate DNA molecules based on density alone. Using this technique, Meselson and Stahl were able to physically separate denser 15N strands containing bases enriched with 15N from DNA from lighter strands containing bases composed of 14N and thus provided them with what they were looking for, a means to examine the replication of DNA.

isopycnic

Meselson and Stahl devised a classic experiment, using the new technique of ____ labelling, that distinguished between three alternative models for DNA replication that had been proposed.

isotopic

The lytic and lysogenic life cycles of the T2 Phage, in the lytic cycle, the cell ____ releasing phages

lytic

Inclusions: Granules, crystals, or globules of organic or inorganic material that are stockpiled by the cell for future use. Some are enclosed by a single-layered membrane. •Membranes vary in composition. •Some made of proteins; others contain lipids. •May be referred to as ______.

microcompartments

Hershey and Chase found that when the bacteria had been infected with T2 phages that contained radiolabeled proteins (35S), most of the radioactivity was in the supernatant that contained phage particles, ____in the pellet with the bacteria. When they examined the bacterial cultures with T2 phage that had radiolabeled DNA (32P), most of the radioactivity was in the pellet with the bacteria.

not

The ____: -Usually not membrane bound (few exceptions). -Location of chromosome and associated proteins. -Usually 1 closed circular, double-stranded DNA molecule. -Supercoiling and nucleoid proteins (different from histones) aid in folding

nucleoid

The location of a gene's promoter relative to _____and to the sites where the DNA attaches to the chromosome scaffold or nuclear lamina can affect whether the gene is transcribed. Genes of densely condensed heterochromatin are usually not expressed, presumably because transcription proteins cannot reach the DNA. A gene's location relative to nucleosomes and to attachment sites to the chromosome scaffold or nuclear lamina can affect transcription.

nucleosomes

The Dideoxy Chain-Termination Method for Sequencing DNA 3. The labeled strands in the mixture are separated by passage through a polyacrylamide gel in a capillary tube, with shorter strands moving faster through the gel. A fluorescence detector system senses the color of each fluorescent tag as the strands come through. Strands differing differing by as little as ____ nucleotide in length can be distinguished.

one

The basic mechanism for the control of gene expression in bacteria, known as the _____ model, was described by Francois Jacob and Jacques Monod in 1961.

operon

Flagellum rotates like a ____. •Very rapid rotation up to 1100 revolutions/sec. •In general, counterclockwise (CCW) rotation causes forward motion (run). •In general, clockwise rotation (CW) disrupts run causing cell to stop and tumble.

propeller

The T2 phage, consisting almost entirely of DNA and ___, attacks Escherichia coli (E. coli), a common intestinal bacteria of mammals. This phage can quickly turn an E. coli cell into a T2 -producing factory that releases phages when the cell ruptures.

protein

In Chemotaxis, behavior of attractant/repellant, tumbling frequency is ____ ; runs toward/away from compound are longer.

reduced

DNA methylation ___ gene expression.

reduces

Histone modifications ____ gene transcription.

regulate

_____ are complex protein/RNA structures. •Sites of protein synthesis. •Bacterial and archaea ribosome = 70S.

ribosomes

FtsZ—many bacteria. •Forms ____ during septum formation in cell division.

ring

The motor that drives flagellar rotation is located at the base of the flagellum. Torque generated by the motor is transmitted to the hook and filament. The motor is composed of two components: the ____ (the moving parts) and the stator (the stationary components).

rotor

In 1958 Mathew Messelson and Franklin Stahl demonstrate the _____ replication of DNA.

semiconservative

In the ____ model, The two strands of the parental molecule separate, and each functions as a template for synthesis of a new complementary strand.

semiconservative

The Dideoxy Chain-Termination Method for Sequencing DNA 1. The fragment of DNA to be sequenced is denatured into _____ strands and incubated in a test tube with a primer designed to base pair with the known 3'end of the template strand, DNA polymerase, the four deoxyribonucleotides (dATP, dCTP, dTTP. dGTP) and a lower concentration of the four dideoxyribonucleotides (ddATP, ddCTP, ddTTP. ddGTP) each of the dideoxynucletides tagged with a different fluorescent molecule.

single

The tryptophan operaon- Regulation of a Metabolic Pathway Escherichia coli synthesizes tryptophan from a precursor molecule in a series of steps, with each reaction catalyzed by a specific enzyme. The five genes coding for these enzymes are clustered together on the bacterial chromosome as a transcription unit, served by a ____ promoter. In the case of Tryptophan in E. coli, an abundance of tryptophan can (a) inhibit the activity of Enzyme 1 (i.e.) feedback inhibition, a rapid response, and (b) repress the expression of the genes encoding all subunits of the enzymes involved in the pathway, a longer term response.

single

The Dideoxy Chain-Termination Method for Sequencing DNA 4. The color of the fluorescent tag on each strand indicates the identity of the nucleotide at its end. The results can be printed out as a ____ and the sequence determined

spectrogram

____ is the process of endospore formation. -Occurs over several hours. -Normally commences when growth ceases because of lack of nutrients. -Complex multistage process

sporolation

Eukaryotic gene expression can be regulated at any ____ .

stage

In the cell, ___ determines function.

structure

_____ occurs on moist surfaces as a type of group behavior by bacteria. -Most swarmers have peritrichous flagella. -Production of molecules that aid movement is typical.

swarming