Which media should not be autoclaved?

Which media should not be steam sterilized and why? Examples of culture media that are not steam sterilized are Selenite Cysteine Broth, Tetrathionate Broth, Bismuth Sulfite and Hektoen Enteric Agars. Autoclaving as well as boiling longer than needed destroys the selectivity of the medium.

Which solution helps in differentiation raw cotton for absorbent cotton?

Ammoniacal copper oxide solution dissolves raw cotton fibres with the formation of balloons. While absorbent cotton dissolves completely with uniform swelling. Cotton is insoluble in dilute sodium hydroxide solution and hydrochloric acid. It is soluble in 66 % of sulfuric acid.

Who discovered cotton plug in microbiology?

George Schroeder and Theodor Von Dusch (1854) were the first to introduce the idea of using cotton plugs for plugging microbial culture tubes.

Why are petri dishes incubated upside down?

Petri dishes need to be incubated upside-down to lessen contamination risks from airborne particles landing on them and to prevent the accumulation of water condensation that could disturb or compromise a culture.

Why is agar a better solidifying agent than gelatin?

One advantage of agar was that no organisms of medical importance could digest it. The use of gelatin as a solidifying agent had been discarded precisely because so many bacteria could break it down, hence turning a solid medium into a liquid on.

Why must agar be cooled to 50 degrees?

The sterile agar is then allowed to cool to 50 °C: this is just above the setting point of agar and pouring at this cooler temperature helps prevent condensation forming on the lid.

Why must loops be cooled first?

Flaming after use kills any bacteria left on the loop from your bacterial transfer activities. Why must the loop be cool before you touch it to a culture? … If the loop is still hot when it touches the bacteria, it will kill it. You should not set it down to cool, as this can contaminate the loop.

Why must the loop be flamed?

Flaming after use kills any bacteria left on the loop from your bacterial transfer activities. Why must the loop be cool before you touch it to a culture? … If the loop is still hot when it touches the bacteria, it will kill it. You should not set it down to cool, as this can contaminate the loop.

Why pour plate is more accurate?

Advantages of Pour Plate Technique Will detect lower concentrations than surface spread method because of the larger sample volume. It requires no pre-drying of the agar surface. The most common method for determining the total viable count is the pour-plate method.

Why should tube caps be held in hand during inoculation?

Inoculating loops, inoculating needles, and forceps. … During transfer, the cap must be held in the same hand as the inoculating loop or needle. Why should test tube caps never be placed on the bench? To prevent contamination and interfering with the bacteria or culture you are working with.

Why should you keep test tube lids on your inoculated cultures for incubation screwed on loosely?

Leave the lid loose on your slant so that the bacteria have access to oxygen.

Would anaerobic bacteria grow in a pour plate?

Viable anaerobic bacteria are quantitated by the fractional gram pour plate technique under an anaerobic atmosphere. Caution must be exercised when applying the method since isolates may be pathogenic.

Why cloth absorbs water?

Cotton is pure cellulose, a naturally occurring polymer. Cellulose is a carbohydrate, and the molecule is a long chain of glucose (sugar) molecules. If you look at the structure of a cellulose molecule you can see the OH groups that are on the outer edge. These negatively charged groups attract water molecules and make cellulose and cotton absorb water well. Cotton can absorb about 25 times its weight in water. Chemists refer to substances like cotton as hydrophilic, which means that they attract water molecules.

Are cloth diapers waterproof?

The waterproof outer portion of the diaper is going to be either PUL (whether you pronounce that as “pull” or “P-U-L” is totally up for debate) or TPU. These are both just laminated polyester fabrics that are waterproof.

Can cotton canvas get wet?

Traditional cotton canvas is waterproof in the same manner that traditional wooden boats are waterproof. The cotton fibers — like the wooden planks — swell when they get wet.

Can fabric be made waterproof?

To waterproof natural fabric like cotton, denim, or canvas, give it a thorough rubdown with a bar of Otter Wax. The wax won’t leave any residue, but will stiffen and darken the fabric to give it a rugged appearance: We recommend denim shirts, work jackets, and old canvas weekenders.

Can viscose be ironed?

Viscose should be ironed on the reverse side when it is still wet. We recommand you to select the program « Silk » or the iron at one dot (110°C). And for more precaution, you can use a damp cloth.

Can you iron modal fabric?

Ironing. Some modal garments, depending on how they’re woven and constructed, may wrinkle excessively when washed and will require ironing. Use a medium-hot iron, and always iron on the opposite side of the fabric to prevent creating a shiny spot on the surface of the clothing.

Can you wear cotton in rain?

Avoid cotton fabrics as much as possible Cotton is highly absorbent which makes it heavier when it gets wet. … It is such an irritating feeling to be wearing wet cotton fabric since it does not dry easily and will keep you wet even when rains stop.

Does canvas breathe?

Canvas Tent Breathability Unlike plastic tents, canvas allows small moisture particles from breath, sweat, and cooking to escape directly through the tent fabric.

Does cotton have plastic?

No, most likely it doesn’t. We identified four areas in which hidden plastic is used in garments. And when you look around you’ll note that this hidden plastic is unfortunately in almost all garments, also in ours at the moment.

How can you make fabric waterproof?

In general, use a ratio of 2:1 wax to drying oil. Once the mixture begins to harden, use a spatula or popsicle stick to spread the mixture on the fabric you want to waterproof. Use a fabric made of natural fibers; natural fibers such as cotton are hollow, which allows them to absorb the waterproofing mixture.

How is fabric made waterproof?

The process involves coating a layer of polymeric material on one surface of the fabric. The fabric is passed over a roller where a liquid coating is poured over the roller, and the fabric is then passed through a dryer, followed by having it pass through an oven to solidify the coating.