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26

Vibrio cholerae is known to have two circular chromosomes. Bacteria cell division is a lot simpler and efficient as compared to eukaryotic cell division, partly due in part to the nature of their chromosomes. They don't have to undergo mitosis -- condensation of chromosomes, segregation, spindle fibre formation, attachment et al aren't involved in bacterial ...


19

Bacteria usually gain resistance mechanisms through horizontal gene transfer (such as conjugation and phage infection). The four main mechanisms in which bacteria elude antibiotics are: Drug Inactivation: For example, E. coli can produce beta-lactamase that inactivate many lactam based antibiotics such as penicillin. Alteration of Target Site: Mutations in ...


17

To expand a little bit the other answer, I would also add that bacteria can have other (usually circular) DNA segments aside from their main chromosome. These are called plasmids and are double stranded molecules of DNA that can replicate autonomously. Plasmids often carry genes that allow an organism to survive in certain conditions, for instance they ...


15

No There are several reasons why this might not be true, as Alexander has discussed. An antibiotic often has a molecular target that isn't present in all bacteria, it's extremely hard to get antibiotics to certain parts of your body, and some bacteria will be defended against a antibiotic attack by biofilms, resistance mechanisms, and sheer statistical ...


14

Growth can be quite slow for some species under certain conditions when the concentration of cells is too low. Log-phase growth is powerful, and so one would like to keep cells in this state for the experiment at hand. Different genes are expressed then compared to a stationary phase. In addition, you'd like your culture to out-compete a contaminant if ...


14

Bacteria have a mesh-like structure surrounding their plasma membrane called a cell wall. The cell wall is made up of peptidoglycan polymers that form a rigid crystalline structure that helps protect the osmotic pressure of the bacterial cytoplasm. Penicillin and other β-lactams work by inhibiting the final step of peptidoglycan synthesis, which ...


14

Simply put, old habits die hard; physicians and other medical personnel have grown up with the old species designations so will continue to use them. This is somewhat the reverse of the case with E. coli, where 80-90% of the genome is variable across strains. Lin-Hui gives a brief history, where strains identified early were given specific names within ...


13

Just a quick answer: No, there is no way to kill all bacteria in your body once they are there. The only way to keep a person sterile is to prevent any bacteria entering the guts during and all time after the birth. Look for gnotobiology and gnotobionts to learn more about these organisms (including humans). Here are some reasons why: Most antibiotics ...


13

You can find a detailed discussion of this topic here. Magnetic bacteria contain chains of magnetic crystals (magnetite or greigite) which cause the cells to be oriented in a magnetic field. It was originally proposed that magnetic bacteria use their magnetosomes to ensure that they swim downwards into the sediment (everywhere on earth, except at the ...


13

First, and I cannot stress this enough, you should not go seeking out human pathogens if you don't have the appropriate equipment to handle it at the right safety level. That goes for all pathogens, even ones you might find around your house. In a professional lab, you might get samples from collaborators, clinical samples, vendor, or really an number of ...


12

Also, what research is being conducted to combat bacteria resistant to antibiotics? You've gotten some decent answers for how antibiotic resistance arises, so I thought I'd touch on this a bit. There's three major thrusts to anti-resistance research: Finding new targets and mechanisms. Essentially, creating new antibiotics that are subtly different ...


11

I think the current answer to this for bacterial infections is quorum sensing. Quorum sensing is a signalling pathway in bacteria which senses a molecule that the bacteria themselves secrete. When the concentration of the quorum signal reaches a certain level, the bacteria interpret this as their population density reaching some threshhold. Bacteria are ...


10

Most of the initial colonisation is said to be coincidental ('happenstance' as the textbook puts it!) exposure. It's then fairly predictable depending on: type of delivery (as Larry commented); feeding; and receipt of antibiotics. In terms of feeding, there are differences in flora between babies fed human milk and those that are given cow's milk. ...


10

I think that cells get damaged at -20°C not because they are stored for a long period of time, but because they undergo cycles of thawing and freezing (the ice crystals that form damage them). I never keep cells at -20°C. I store them at -80°C in 50% glycerol. The idea behind the glycerol is that it serves as cryoprotecor. It forms hydrogen bonds with the ...


10

The lead question you have answered yourself: bacteria become resistant because of the selection pressure caused by the antibiotic's effective suppression of the original non-resistant bacteria. Those variants which resist the suppression are selected for as a natural consequence. How do resistant bacteria process antibiotics? It depends on the details of ...


9

There are a number of ways to address antibiotic resistance in infectious bacteria. What one gets used depends on exactly what organism we're talking about. But below is a short list of some ways: Changing the antibiotic being used. Not all antibiotics have the same molecular target within a bacterial cell. Some interfere with the formation of the cell ...


9

Mitochondria are very similar to bacteria and are thought to have originated from bacteria. This points you to the answer: bacteria produce ATPs the same way mitochondria do, with the oxidation machinery place in their plasma membrane (analogous to the mitochondrial membrane).


9

Infectious agents like bacteria, viruses, fungi, etc., don't know when to "attack" or produce pathogenic substances, they just do it under their preferred conditions, and your body's immune system either succeeds in fighting them off immediately, or it doesn't and you get sick. Your body is constantly confronting and clearing potentially dangerous ...


8

Gergana covered the "why" part of your question. +1 If all you have at the moment is a -20°C and mostly what you want to store is E. coli harboring plasmids, I'd recommend preparing plasmid DNA and storing that at -20°C. The DNA will stay stable in the medium term, and you can re-transform into E. coli once you've got your -80°C freezer up and running. And ...


8

The donor bacterium, viewed as a unit, may well gain no advantage from sharing its genes. The genes that are shared, however, may gain a very substantial reproductive advantage from being able to spread to other strains. If some of the genes that are capable of being shared also promote sharing, they may be selected for by evolution. This is a good ...


8

An antibacterial is any compound that will kill or at least slow down the growth of strictly bacteria, a domain of prokaryotes. An antibiotic is often used synonymously, but denotes a compound that kills or slows down the growth of any cellular pathogen, prokaryotic or eukaryotic. So, certain antibiotics can kill bacteria, fungi and parasites but ...


8

The hoatzin has a digestive system that makes use of bacterial fermentation. Many other birds also consume grass, e.g. ostriches, ducks and geese. There's also a large body of literature on how birds can digest cellulose.


7

I agree that a starter culture would out-comete a contaminant (especially if there is no antibiotic in the media). Another advantage of inoculating with starter culture is that your results concerning plasmid preps or preparing competent cells will be easily reproducible. By inoculating with a colony, the starter number of cells is different each time you ...


7

The reason that Archaea were determined to be a separate (and only the third) kingdom so late (1977 according to this reference) was because archaea often completely resemble eubacteria. They are unicellular and have no organelles and appropriately they were grouped with other prokaryotes because of their morphology and cellular physiology. But by the ...


7

Reasons for Bacteria with different shapes as given in Wikipedia/Bacteria: The wide variety of shapes is determined by the bacterial cell wall and cytoskeleton, and is important because it can influence the ability of bacteria to acquire nutrients, attach to surfaces, swim through liquids and escape predators. There is an article based on research ...


6

Why is NADH the first thing to come to mind? Time for some physical chemistry. Beta-lactams has a shorter ring structure which give it a different absorbance (around 322 nm apparently (source needed)) which gives it a blueish hue. Typically Penicillin and Ampicillin start off as an off-white. As hinted by @Mad Scientist, the beta-lactam rings are unstable ...


6

If I understand the nomenclature correctly, an R plasmid is just any plasmid containing an antibiotic (R)esistance gene (eg. Amp, Kan, Cm, etc.). It's a bit of an outdated name from when people didn't know how exactly the plasmids conferred such resistance. An F-plasmid is any plasmid that contains the genes necessary for (F)ertility, eg:horizontal gene ...


6

A quick search on ISI Web of Knowledge yielded this paper: R J North, P A Berche and M F Newborg (1981) Immunologic consequences of antibiotic-induced abridgement of bacterial infection: effect on generation and loss of protective T cells and level of immunologic memory. Journal of Immunology 127: 342-346 The authors investigated the effects of ...


6

The Gram stain is one of a large number of techniques used to characterize bacteria. In particular, a bacterial species is usually either Gram-positive (purple when stained) or Gram-negative (pink when stained). In Gram-postive bacteria, the cell wall is thicker and has much more peptidoglycan compared to Gram-negative bacteria. The chemicals in the stain ...



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