Which Organism Survived The Longest Exposure Why


Which Organism Survived The Longest Exposure Why?

megaterium survived the longest because it contains spores which are resistant to heat. Why were you told to remove the plate covers prior to exposing them to UV?

Which of the organisms survived the longest exposure?

Which organism survived the longest exposure? Why? B. subtilis survived the longest because of the presence of spores.

Why are bacterial endospores more resistant to UV light than vegetative cells?

Why are endospores more resistant to UV light than vegetative cells? – The DNA of endospores is protected by small acid-soluble proteins that bind to DNA and alter its conformation thereby protecting it from photochemical damage.

Why were you told to remove the plate covers?

In the lethal effect of ultraviolet radiation on microbial growth experiment why was the lid removed from the plate before exposure to the UV light? Because UV radiation cannot penetrate through plastic.

How long would you like to expose the plate to UV light?

Thus 20-25 minutes exposure to UV light seemed adequate for disinfection and 30 minute exposure time is recommended for UV disinfection. The efficacy of inactivation of various organisms at the distance of eight feet from UV source and exposure time of 30 minutes is shown in the figure.

Is EMB defined or undefined?

Eosin methylene blue agar (EMB) is an undefined medium. EMB is a complex medium consisting of peptone dipotassium phosphate lactose eosin Y (dye) and agar. In Undefined media the exact biochemical composition of the nutrient is not known and provides the growth of wide varieties of microorganisms.

What is the application purpose of MacConkey agar?

MacConkey agar is used for the isolation of gram-negative enteric bacteria. It is used in the differentiation of lactose fermenting from lactose non-fermenting gram-negative bacteria. It is used for the isolation of coliforms and intestinal pathogens in water dairy products and biological specimens.

Why B subtilis is more resistant to UV light?

subtilis are 5 to 50 times more resistant to UV radiation than are the corresponding growing cells. This elevated spore UV resistance is due to: a) the photochemistry of DNA within spores as UV generates few if any cyclobutane dimers but rather a photoproduct (Fig.

What is Fimbriae microbiology?

Fimbriae are long filamentous polymeric protein structures located at the surface of bacterial cells. They enable the bacteria to bind to specific receptor structures and thereby to colonise specific surfaces.

Why are some bacteria more resistant to UV light?

faecium both Firmicutes) were more resistant to UV irradiation than two Gram-negative bacteria (E. … aeruginosa phylum Proteobacteria and Firmicutes respectively) which could be due to the thicker peptidoglycan layer in Gram-positive organisms protecting the cells from UV damage.

Why is it important to remove the petri dish plate covers prior to exposing them to UV?

Why do you remove the cover prior to exposing the dish to UV light? UV light does not penetrate well and can not penetrate the plastic.

What do individual colonies tell you about the cells from which they grew?

What do the colonies tell you about the cells from which they grew? The cells were able to repair the damage caused by UV. What does the relatively heavy growth on the plates covered by the mask and lid during exposure tell you about UV radiation?

Why shouldn’t you connect the data points for each organism in your graph?

Why is it not advisable to connect the data points for each organism in your graph? … account for the inability of organism to grow outside their ph ranges.

Why was there still E coli growth after UV exposure?

The control was the side of plate that was NOT exposed to UV light. Why was there still E. … Coli still has repair mechanisms for UV radiation which is why we saw it have growth will shorter exposure.

What happens when bacteria is exposed to UV light?

In simple terms when bacteria or another type of microbe is directly exposed to certain types of UV light the DNA (its fundamental building block) of the cell is damaged preventing it from replicating. If a cell cannot reproduce then the cell cannot cause infection which is how UV light kills bacteria.

How can ultraviolet radiation limit the growth of microorganisms?

Ultraviolet light inactivates bacteria by forming pyrimidine dimers in DNA which can interfere with transcription and replication.

Would Removing B phenylethyl alcohol from pea?

Would removing b-phenylethyl alcohol from PEA alter the medium’s sensitivity or specificity? It would alter specificity because organisms that “shouldn’t” grow on it would. It wouldn’t likely alter sensitivity because you would probably still be able to detect growth of organisms that “should” grow on it.

Would removing bile salts and or crystal violet from MacConkey Agar alter the medium’s sensitivity or specificity?

How would removing crystal violet from MacConkey Agar alter the sensitivity and specificity of the medium? It would inhibit the growth of gram positive bacteria because this test is used to differentiate the gram positive bacteria and enterobacteria.

What is the role of bile salts in he agar?

Bile salts render the medium selective inhibiting Gram positive organisms and reducing growth of some gram-negative organisms other than Salmonella and Shigella.

Does Staphylococcus grow on MacConkey Agar?

MacConkey agar selects for organisms like Escherichia coli (Gram negative bacilli) while inhibiting the growth of organisms like Staphylococcus aureus (Gram positive cocci).

Why does E coli grow on MacConkey Agar?

By utilizing the lactose available in the medium Lac+ bacteria such as Escherichia coli Enterobacter and Klebsiella will produce acid which lowers the pH of the agar below 6.8 and results in the appearance of pink colonies.

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What is the application purpose of EMB Agar?

In your own words what is the application (purpose) of EMB agar? EMB agar is used to stain gram negative bacteria. It is used to isolate fecal coliforms(G- bacteria rod)*** . It’s used to distinguish between lactose fermenting coliforms and lactose non fermenting coliforms.

What can UV rays do to DNA?

Ultraviolet (UV) light kills cells by damaging their DNA. … The resulting thymine dimer is very stable but repair of this kind of DNA damage–usually by excising or removing the two bases and filling in the gaps with new nucleotides–is fairly efficient.

Why did Bacillus subtilis survive longer than Escherichia coli when exposed to UV light?

Why do Bacillus subtilis cultures often demonstrate more growth than Escherichia coli on plates that were exposed to equal amounts of UV light? B. subtilis has thicker walls that protect the cells from UV. … subtilis can produce endospores which are resistant to the effects of UV.

Is E coli resistant to UV light?

When UV light is experimentally used as a selective factor in E. coli natural resistance to this agent is commonly increased making this response an excellent model to study the kind and recurrence of genetic changes associated with the emergence of a particular phenotype.

What is glycocalyx made up of?

The glycocalyx which is located on the apical surface of endothelial cells is composed of a negatively charged network of proteoglycans glycoproteins and glycolipids.

Do all bacteria have ribosomes?

Ribosomes – Ribosomes are microscopic “factories” found in all cells including bacteria. They translate the genetic code from the molecular language of nucleic acid to that of amino acids—the building blocks of proteins.

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Is Fimbriae prokaryotic or eukaryotic?

A fimbria (plural: fimbriae) is a type of appendage of prokaryotic cells. These hair-like protrusions allow prokaryotes to stick to surfaces in their environment and to each other. Longer appendages called pili (singular: pilus) come in several types that have different roles.

Can bacteria survive radiation?

Deinococcus radiodurans is an extremophilic bacterium and one of the most radiation-resistant organisms known. It can survive cold dehydration vacuum and acid and therefore is known as a polyextremophile.

What bacteria is UV resistant?

Deinococcus radiodurans was the most resistant bacterium to both types of radiation with a D37 value of 4.0 × 104 μWs cm2 to UV light and 300 krads to gamma radiation.

What type of radiation is UV?

Ultraviolet (UV) radiation is a form of non-ionizing radiation that is emitted by the sun and artificial sources such as tanning beds.

What is the purpose of exposing the plates to UV radiation?

Why did we expose spread plates to UV light for varying times? UV radiation is lethal because of its mutagenic properties. When DNA absorbs UV light it causes the formation of pyrimidine dimers which form when a covalent bond forms between two adjacent thymine or cytosine molecules in a strand of DNA.

How long would you like to expose the plate to UV light quizlet?

Place plate A under the UV lamp. Remove the lid from the plate and cover half of the plane with an index card. Turn on the lam and expose the plate for 30 secs. Make sure you are wearing goggles and to not have your dads under the lamp.

Why would we need to expose the Serratia and the bacillus to UV radiation for different amounts of time to achieve sterilization?

–Serratia marcescens are very sensitive to UV light and mutation can occur quickly causing cell death. –Bacillus has endospores therefore it needs to be exposed to UV light for an extended period of time to see any effect.

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