What would be the worst weaponized bacteria or virus?

Answered Dec 28, 2018

Biological weapons have existed for many years.

In the middle ages, an attacking army would use siege engines to catapult corpses of animals and humans who had died of various plague diseases, over the walls of castles and fortified cities.

Two future versions come to mind.

First is an intense, but short term strategy.

You would want something which spread very easily, and killed people quickly. However, you might want to occupy the geographic area afterwards, and so need some way to keep your own soldiers and colonists safe.

With a virus, you would need an enveloped influenza. They spread easily, but also degrade quickly when sitting on a surface, or exposed to air.

With a bacteria, you would need something with multi-antibiotic resistance genes (that you could insert, and/or select for). However, you would also need to have either a better antibiotic (to give to your own occupying people), or some way to turn off the resistance genes (with drugs, or chemicals that you spray on surfaces, etc). Drug development is time-consuming, so your opponent could be working on it simultaneously. Turning genes on/off is complicated, even in controlled lab conditions.

Second, would be a “salt the earth” strategy. Which would be easier and simpler.

This means not only killing everyone in the target area, but also never occupying it, or using it. For this, you need a spore-former. Such as Bacillus anthracis – Anthrax. Or something in the same category, but even more obnoxious. These can last for decades in a harsh desert, and then sprout and kill in human-friendly conditions.

A third possibility is indirect. Humans are dependent on animals and plants for food.

Some microbes will target animal livestock, or will target food-crop plants. You could use either bacteria or fungus, depending on your exact target and timeframe.

This isn’t a bullet that can only be shot once, at one target. It isn’t a bomb that explodes, and then you never hear it again.

Biological weapons will be quite happy to turn on their alleged makers.

What are the diseases caused by bacteriophage viruses?

Answered Dec 26, 2018

As the name suggests, bacteriophages infect bacteria. They cannot infect humans, other animals, or plants.

However, some phages have genes that code for peptide toxins, which are then released by the bacterium host.

So the phage infects the bacteria, and provides the genetic information to produce the toxin. When you get infected by the bacteria (e.g. from contaminated water or food), it releases the toxin, which makes you sick.

This is kind of a symbiotic relationship between the phage and the bacteria species. The phage gets to spread and reproduce itself, and the bacteria receives information to become more virulent. When the toxin induces diarrhea, that helps to spread the bacteria host and the phage inside it.

Human diseases involving phage coded toxins include botulism, cholera, diphtheria, scarlet fever, and a few others. Here is a list.

To what extent does nature select for simplicity?

Updated Aug 11

Selection tends to be a numerical issue. It is largely about who survives their environment long enough to reproduce efficiently. Which leads to large numbers of progeny and descendants.

Without getting into a debate as to whether they are “really alive”, the most numerous species on the planet are bacteriophages. They are viruses which infect bacteria. They are very small, and relatively simple (although they are actually more complex and elegant than they seem at first).

The next most numerous are bacteria and archaea, which are comprised of single cells. These domains contain a range of species that can survive a very wide range of environments. Each individual species has its own needs, but, as general groups, bacteria and archaea can be found in many places that more complex life forms cannot.

Simplicity vs complexity relates to the amount of time and energy that is required for replicating yourself. A human being takes nine months, while bacteria have a theoretical minimum of 20 minutes (although, in reality, it tends to be somewhat longer, like maybe an hour, depending on conditions). The required energy and nutrients are vastly less per new bacterium.

Some species can evolve towards being more simple. If you are a microbe in an environment where certain needed molecules are plentiful, then you can lose the genes that code for enzymes to make those molecules yourself. Then, replicating yourself takes less time and resources, so you are now more efficient.

Microbes were around for a very long time before humans, and will continue long after we are gone.

Some multicellular organisms are also advantaged by relative simplicity. There are far, far more insects than there are mammals, for example. Also, their progeny are independent immediately, rather than needing years of parenting, sexual development, etc.

Can we say that the relationship between a bacteriophage and a bacteria is parasitism?

Updated Jul 13

Not always.

Some phages may be aggressively lytic (such as T4), and are possibly just parasitic.

However, phages that are slower-acting, and are present for an extended time period without killing the host, may have some kind of beneficial contribution.

The CTXφ bacteriophage infects Vibrio cholerae. The phage DNA is spliced into the host chromosome (as a “prophage” which isn’t necessarily making any new particles at the moment).

CTXφ contains the gene which codes for the cholera toxin, That toxin is what induces a human to have massive diarrhea during a cholera infection. That spews out lots of Vibrio cholerae, thereby helping the host to spread.

There is the Ff family (f1, fd, or M13), which keeps its genome separate, but secretes copies of itself without immediately lysing the host. I have read a couple of obscure mentions of some metabolic changes in the host. Although I don’t know if they are beneficial in any way.

I think another possibility is Lambda λ, which integrates as a prophage, which protects against further infection by any more Lambda λ copies. I suspect that maybe it also protects against other, more aggressive phage species.

Also, phages might be beneficial in the big picture. When prophages are being copied, the process isn’t perfect, and sometimes short segments of adjacent host DNA sequences are accidentally packed into new phage copies. This may result in horizontal gene transfer. That genetic information from the dead host is then injected into other bacteria.

What is the most primitive organism living today?

Updated Jun 8

If they are alive on Earth today, then none of them are primitive.

Every species currently existing is a product of billions of years of evolution.

A small, relatively simple, single-cell microbe species will be highly adapted to its particular environment. They can thrive just fine, live out their lives, create progeny, etc.

They replicate very rapidly, and, as a species or a strain, can adapt fairly rapidly to changes.

A species can even evolve by simplifying itself. If you live in an animal’s gut, you might lose the genes to make certain molecules which are plentiful in that environment. You would actually become more efficient, and thus, more evolved.

Unicellular organisms may seem “primitive” from a very basic view, but they start looking very complex when you look closely enough. This applies to individual cells, and to populations of individuals interacting with each other.

It’s very much about context.

There are plenty of single-celled bacteria and archaea which thrive in environmental conditions which would kill a human very quickly and painfully.

From humans’ perspectives, microbes may seem primitive and inferior. From some microbes’ perspectives, humans are clueless, enslaved providers of food, shelter, and transportation.

Perhaps one of the most “primitive” organisms on Earth are those zombies who devote their biological structures, processes, energy, and time, to alternately watching reality television, and then compulsively staring at their phone to scroll through FaceBook.

Can virus and bacteria survive in salt water?

Updated May 11

The keyword is “halophile”. Like other types of extremophiles, most of these are in the domain Archaea, which are kind of like bacteria, but kind of different.

The issue with salt water is that, a high concentration of sodium chloride in the surrounding water environment, might suck out the water that is inside the cell. That is called “osmosis”.

A way to avoid this is to have a compensating solute inside the cell, which does not have to be sodium, and can be a range of other things. Those substances keep the water inside the cell from being sucked out. It takes energy and certain genetic information to do this.

It isn’t exactly a matter of just “surviving”. They are adapted to their environment, and actually need it.

If you took them out of their normal high-salt water environment, and put them into distilled water (theoretically zero salt) they would die. A similar issue exists for hyperthermophiles, which would freeze to death at room temperature. These are some reasons why culturing and studying extremophiles is a major hassle.

As for viruses, they don’t “survive” anything, because they aren’t technically alive in the first place.

A virus may have a protein coat (capsid), which might be disrupted by a high-salt environment. However, as with bacteria, some species may be quite happy with it.

Some other viruses are “enveloped”, and are coated with part of the membrane of the host cell that they had infected and escaped from. Those are a lot more fragile, and may be deactivated just by sitting around exposed to the air for awhile (e.g. that cold/flu virus that sat on the elevator button for a couple of days). So I would expect those to be vulnerable to every threat, including high salt.

Fun Fact #1: “Salt” doesn’t just mean sodium chloride table salt. It really relates to ionic compounds, like a metal and a non-metal.

Fun Fact #2: The most abundant biological unit on Earth is bacteriophages. They are viruses that infect bacteria, and the oceans (salt-water) are full of them. I only really know a lot about one (1, n=1, a single, solitary one) virus, and it is one of these, and apparently quite durable in many environments.

Why don’t we use the antibodies of recovered patients to treat antibiotic-resistant bacteria? We spend time developing new, chemically synthetic, small molecules as new antibiotics to treat the previously untreatable resistant bacteria.

Updated Mar 20

Thanks for the A2A.

As I recall, when your body produces antibodies in response to an infection, it tries out a very large number of randomly-generated antibodies. When one of those random ones “fits” onto the surface of the microbe, then your body starts producing more of that particular antibody. You can make a range of antibodies which fit onto different surface features of the microbe.

Those antibodies that work to help clear the infection are very specific to the microbe that you have.

If you took your antibodies from your blood and purified them, the process would be resource-intensive, and expensive. Also, the new patient may be infected with a microbe that is different to yours, so your antibodies won’t fit onto it. Even the same species can have mutations that will prevent the binding.

Some viruses are particularly rapid with these mutations, and can do it during the infection of one person. HIV does this, which is one of a few reasons why a vaccine is so difficult to make. It becomes a “moving target”.

I’m not sure of the level of risk that, antibodies transferred from one individual to another would be viewed as foreign enough to trigger a negative reaction. In scientific research, there are “secondary” antibodies available, that bind to other antibodies, but these are produced by a process involving two different species of animals (e.g. a rabbit and a goat).

Some gamma globulins are occasionally administered, in limited contexts. Also, a new mother’s first dose of breast milk contains some immune components, although only a small amount will get through to the infant’s bloodstream, and for a short time period after birth.

Speaking of which, antibodies are proteins, so (unless you are only a couple of days old), your digestive system will chop them up into very short peptides before absorption into your bloodstream. That makes it impossible to take them in a pill, and they would need to be injected, instead.

There is another peptide-based possibility being studied, called bacteriocins. They are made by bacteria to attack each other, and the mechanisms are not yet understood. They are apparently fairly narrow-spectrum, and you still wouldn’t be able to take them orally.

Conventional antibiotics work on a range of different microbes (including narrow-spectrum and broad-spectrum drugs). There are a few general mechanisms. Some disrupt bacterial cell walls, some disrupt bacterial protein synthesis, etc. You don’t necessarily even need to know the exact species causing the infection.

Antibiotics are often used in a prophylactic (preventative) effort. You might have an injury, or a surgical procedure, where you don’t have any infection (yet), but there is a risk, and you need generalised protection. In my experience, penicillin derivatives seem to be the standard choice in that situation.

In order for phagocytes to consume pathogens, they release pseudopods to engulf the pathogen. How do phagocytes do this, do they have some kind of muscle or is it something within the cytoplasm?

Answered Jan 26

Pseudopodia are sort of like fingers that form and sort of blob out of the surface of the cell that is making them.

Inside the cell, there is always a sort of girder-like supporting structure/network called the cytoskelton. This gives the cell physical support and shape, a bit like a person’s skeleton.

However, the cytoskeleton can grow or shrink very quickly, and can be made to grow in a certain place and certain direction, as needed.

The cytoskeleton is partly made of a building block called actin. It is a protein that can be stacked into long strings. Stacking it in a certain way causes the pseudopod “fingers” to poke outwards. Kind of like growing a new arm, just because you needed one at that moment.

Later, the actin filament gets taken apart, and the pseudopod shrinks back.

In your muscle tissues (where the components are more fixed in place), actin is partnered with another protein called myosin, to do contraction (pulling). There, the strings sit there parallel to each other, and contraction is a sliding motion (the chemical and mechanical actions are somewhat complicated).

In the phagocytes, there is a further process called (strangely enough) phagocytocis, in which your cell pulls in the pathogen, and puts it into a vesicle (like a bag) where the pathogen is dissolved by enzymes. This involves proteins on the cell surface pulling a small area inwards, to form the vesicle.

Some other cells, like amoeba stages of some single-cell protozoa organisms can also use pseudopodia to reach out and pull themselves along (similar to crawling).

What is the best YouTube channel to study microbiology?

Answered Dec 20, 2017

Thanks for the A2A.

On YouTube (or the internet in general), there isn’t just one single resource that I can recommend.

However, I have a page of links for science students (of all levels) at:

Links For Science Students

Please excuse the formatting, as I still need to work on that. However, these are the best links that I have found so far, and are somewhat categorised by field of study, with a few comments.

This page will improve in the near future, but generally, these are the links that I have appreciated, for biology, biochemistry, chemistry, mathematics, and , of course, microbiology.

Where did the first bacteria on earth come from?

Answered Dec 16, 2017

Thanks for the A2A.

The answer is (drum-roll, please…)

Nobody knows.

It was a really, really long time ago.

Perhaps, somehow, a little bubble in the water on a beach got some amino acids and nucleic acids (specifically RNA) into it. Those molecules may have formed from water (containing various stuff dissolved in it) dripping onto a rock that heated and cooled off each day.

Perhaps it arrived, frozen in the ice of a comet or meteorite, from some other planet.

Nobody knows, and there is probably zero way for anyone to ever know.

That sounds kind of “zen”, doesn’t it?