Answering "Describe a method to rapidly identify Enterobacteria"

And the answer is The Indole Test, a test that makes use of the capacity certain bacteria have to metabolise the amino acid Tryptophan using a series of intracellular enzymes. This results in the release of a substance known as Indole that is therefore combined with a reactive agent that might accuse colour change.

And how exactly is this accomplished?

For a facultatively anaerobic organism like E. coli all they do is conduct an exothermic reaction to force a reductive deamination (release of -NH2) of the Tryptophan with the aid of the enzyme Tryptophanase (and the coenzyme factor Pyridoxal phosphate). They mix all these very well in their internal blenders and the result is theformation of three main elements:

- Ammonium

- Pyruvic acid

- Indole!

Than all we have to do is join the indole produced with an agent containing a mix of HCl and p-dimethylaminobenzaldehyde in amyl alcohol - nothing much!!, if you can say this long description p-dimethylaminobenzaldehyde in amyl alcohol, you're half way through to get it over the counter... Hahah! Actually this very long-named substance is an organic compound, shall we call it a 'floater' (not water soluble)!!!

And than, bammmmmm, the solution changes colours from yellow to red in a positive treatment. The red solution will top the remaining layers in an indole positive treatment whereas in your negative control (no indole present) it will remain yellowish.

Simples!

The Indole test protocol [1] can be found here thanks to the contribution of Sagal Aryal.

[1] Indole test, Microbiology Notes, [http://www.microbiologyinfo.com/indole-test-principle-reagents-procedure-result-interpretation-and-limitations/], last visited on the 15th of October 2015, last published on the 6th of September 2015.

Image taken from [1].

Describe a method to rapidly identify Enterobacteria

Can you name and describe a method that is used for rapid identification of Enterobacteria (not only the pathogenic ones but also the harmless symbionts)?

I'll give you three clues. Coal, Tar, Faeces.

Image taken from Jarret Morrow M.D., [http://jarretmorrow.com/?attachment_id=1473].

Answering "Name and Describe three types of plasmids"

Plasmids are to bacteria as purses are to women. But if you're one of those extremists that distill every statement then let me rephrase it. Plasmids are to bacteria as watches are to men. Why?

Because when women and men carry purses or watches, respectively, they gain a whole lot of properties, capacities not shown before. They bring up their outfit colors, make them look younger, offer them more confidence, provide them with resistance to a lot of eminent issues like space for meds, documents, mascara and other paraphernalia, or just kind of 'elevate' their social status. Purses and watches basically make a woman/man feel empowered, stronger, more able, even if that is just a temporary property. The wrong purse/watch though will downgrade the carrier to an image of sloppiness others see as an inappropriate taste for fashion, thus unmasking their incapacity.

These circular rings of DNA (plasmids) confer characteristics to the bacteria by adding properties to their genotype that can, eventually, propagate to their phenotype. But how many types of plasmids are there? Well, this question is so redundant that the best way to answer it is with a blunt straight answer. Many I'd say, but we could reduce all those not to three as initially proposed, but actually to five very important classes. But let me twist the example given before and throw out the pursues and watches once for all. Lets talk about plasmids as military roles, I guess it will help us understand their these different classes a bit better:

Resistance plasmids, also known as R-factors, these are the most common ones in the laboratories worldwide spread. These are plasmids that attribute their carriers different resistances to antibiotics, toxicants, poisons etc! We could call them the shield-division for they really stand against the toughest of the environments and give their bacteria protection to a lot of chemical harm.

Virulence plasmids are potential weapons of mass destruction! It's like a really skinny dude taking a bunch load of steroids, Suddenly they make this crazy weak bacteria perform like a Dwayne Johnson. They can make any bacteria a pathogenic liability by conferring them the means to produce some harmful substances.

Fertility F-plasmids, also known as conjugative plasmids or F-factor - of around 100 kilo-bases of length, they hold their own origin of replication and origin of transfer, so they are empowered to 'decide' when and if conjugation will happen. They are the intelligence gathering, the sexy 007 spies. They result in the expression of sex pili that transfers DNA between bacteria. As you can see they're a very avant-garde bunch in the world of DNA transfer.

Conditional plasmids are a sub-division of the military bacterial paraphernalia. They only act when triggered to by different and specific conditions like temperature, for example. When prompted to act they will then produce whatever is written in their artificial genetic code, whether it is producing a certain protein or just protect against a certain antibiotic, you name it, you're the boss.

Degradative plasmids are the fat guys that really want to be part of the army but have no physic to do it. So they just get hired to work in the kitchen and now and then enable bacteria to digest substances that are not very typical in the bacteria's environment. It's like you don't know how to eat a raw potatoe, these fat guys will slice it for you, cut it in little stripes, fry it and salt it and then serve it to you like a freakin' awesome gourmet dish!

Col plasmids, or shall we 'col' them the snipers. They help bacteria produce proteins (bacteriocins), like for example colicin, that will kill other bacteria, point blank. They are indeed very 'col' assassins. I guess that's enough punning! I'm 'col' if you are too, heheheheh.

Have a wonderful day!

1st image taken from Cell meets plasmid, Deviant Art, [http://velica.deviantart.com/art/Cell-meets-plasmid-151423037].

2nd image source unknown.

Name and describe three types of plasmids

We start today a brand new label on the vast catalog of The Toxicologist Today - the ToxicQuizz, with loads of science and loads of humor included, too. Good news is that there is no competition for all is about learning with enthusiasm. And there aren't prizes also for crisis affects us all. But I'll give props to all of you who at least participate. With that in mind rest assured that any right answers can always be more complete with the adding of knowledge posted here by you and your lab mates. Help us make it a funny and insightful tag then.

Shall we start with the first one?

Name and describe at least three types of plasmids

Image kindly taken from Pinterest - author unknown [https://www.pinterest.com/pin/516295544754572929/]