Evolution?

[Naraoia]

But I guess the sigma factor is too small (in size) to affect the morphology of a bacterium.

Size doesn't matter in this case.

MicroRNAs are tiny compared to any protein, but they affect morphology in very important ways. They suppress the expression of some Hox genes, for example.

(Hox genes are part of the apparatus that, put simply, makes your front end different from your back end.)

The proteins made from Hox genes are transcription factors, and so are sigma factors. They switch other genes on. So for all I know about sigma factors (very little apart from this) they could influence the shape of the bacterium.

 

[juvenissun]

How did you come to that strange conclusion by looking at images of very different shaped bacteria?

All three images show bacteria with rounded-corner equant shapes. (different size, though)

 

[juvenissun]

So would I need to be guided by the Holy Spirit in order to understand that living organisms like plants are not really alive? Or do you have some other explanation?

I do. But this is not the place to talk about it.

 

[juvenissun]

As is probably 99% of the non-bacteria.

Face it, what you're looking at (animals, more specifically mammals) is not the norm.

Not knowing the detail, I do believe that.

But, why are we in charge over the majority of, in fact, all, other lives? According to a principle of evolution (the majority is the fittest?), we should be ruled by bacteria or other type of single-cell lives. However, our immune system beat them pretty solidly.

 

[juvenissun]

Juvenissun, you seem fixated on the size of bacteria, that they are small. Do you think size dictates something important about evolution? Is it your contention that a polar bear is somehow more evolved than a human or a mouse?

No. But the single-cell vs. multi-cell difference IS still a big problem, right from the OP.

 

[juvenissun]

The images along with knowing the sigma factors were supposed to show how different they can be from each other.

You're just never going to get it, are you?

I won't say never. I am asking questions. Is that enough?

 

[Naraoia]

All three images show bacteria with rounded-corner equant shapes. (different size, though)

Ok, man, you asked for it

These are not bacteria but archaea, but you get the point:

(source: MicrobeWiki page on Haloquadra, formerly Haloquadratum walsbyi)

 

[pgp_protector]

Not knowing the detail, I do believe that.

But, why are we in charge over the majority of, in fact, all, other lives? According to a principle of evolution (the majority is the fittest?), we should be ruled by bacteria or other type of single-cell lives. However, our immune system beat them pretty solidly.

Right, our immune system, the one that conquered AIDS, Smal Pox, Measles, te Plague, The Cold, ect...

 

[Naraoia]

Not knowing the detail, I do believe that.

But, why are we in charge over the majority of, in fact, all, other lives? According to a principle of evolution (the majority is the fittest?), we should be ruled by bacteria or other type of single-cell lives. However, our immune system beat them pretty solidly.

Oh... some of them, certainly. Some of them only antibiotics beat "pretty solidly", and nowadays some of them outwit even antibiotics.

You can also look at the situation from another angle. If a bacterium (or any other pathogen/parasite) kills its host before it could infect other hosts then it's dead. So in the long run most of the bacteria that parasitise us will be ones that can stably coexist with us, not the ones that wipe out a tribe in two days and die with them.

And just so you know, we would have a hard time without bacteria (and without bacteria, animal herbivores would have a really hard time. Most of a plant is cellulose, and AFAIK only some bacteria can digest that). Besides participating in digestion, gut bacteria also protect us from nastier bugs - the pathogenic bacteria just can't get to the juicy bits because our friendly prokaryotes are already there.

 

[juvenissun]

Size doesn't matter in this case.

MicroRNAs are tiny compared to any protein, but they affect morphology in very important ways. They suppress the expression of some Hox genes, for example.

(Hox genes are part of the apparatus that, put simply, makes your front end different from your back end.)

The proteins made from Hox genes are transcription factors, and so are sigma factors. They switch other genes on. So for all I know about sigma factors (very little apart from this) they could influence the shape of the bacterium.

So, if bacteria have various number of sigma factors, should they have MORE variations on morphology than we have seen?

 

[juvenissun]

Oh... some of them, certainly. Some of them only antibiotics beat "pretty solidly", and nowadays some of them outwit even antibiotics.

You can also look at the situation from another angle. If a bacterium (or any other pathogen/parasite) kills its host before it could infect other hosts then it's dead. So in the long run most of the bacteria that parasitise us will be ones that can stably coexist with us, not the ones that wipe out a tribe in two days and die with them.

And just so you know, we would have a hard time without bacteria (and without bacteria, animal herbivores would have a really hard time. Most of a plant is cellulose, and AFAIK only some bacteria can digest that). Besides participating in digestion, gut bacteria also protect us from nastier bugs - the pathogenic bacteria just can't get to the juicy bits because our friendly prokaryotes are already there.

We are in charge of them. If we don't like them, we can get rid of them. But they could not do the same. So, we (rare life) are "better" then the major forms (abundant) of lives on the earth.

 

[Naraoia]

So, if bacteria have various number of sigma factors, should they have MORE variations on morphology than we have seen?

Not necessarily. I said sigma factors could control morphology for all I know. I only know very few things they control (biochemical responses to extreme heat and various other stresses), so I can't tell you if they actually do morphology.

More to the point, the number of sigma factors wouldn't necessarily correlate with morphological variability even if they had something to do with morphology. Take Hox genes; arthropods have only one Hox cluster (containing 11 genes in the fruit fly), we vertebrates have four (total 39 Hox genes in mammals). Yet are we more diverse than arthropods? I couldn't confidently say that.

Morphology is a complex thing that emerges from networks of gene interactions. You can't just take one type of control gene and say "more X factors = more diversity".

 

[Tomk80]

Not knowing the detail, I do believe that.

But, why are we in charge over the majority of, in fact, all, other lives?

We aren't. We interact with them, we aren't in charge of them. Some of them we need, like the bacteria in our gut. Other we try to defend against, but defending against is not "being in charge".

According to a principle of evolution (the majority is the fittest?),

Since when is that the principle of evolution?

we should be ruled by bacteria or other type of single-cell lives.

Wrong again.

However, our immune system beat them pretty solidly.

Depends on the disease and the individual. It's an arms race, not a steady state. And given our need to develop medication, our immune system is far from beating them pretty solid.

 

[Tomk80]

We are in charge of them. If we don't like them, we can get rid of them.

Far as I know, up to now that only has succeeded with smallpox.

But they could not do the same.

Good for them, if they would they'd stop existing as a species, given that they killed our food. I for one wouldn't be so sure that it isn't bacteria harvesting us instead of vice versa.

So, we (rare life) are "better" then the major forms (abundant) of lives on the earth.

If we kill them, we die. How are we better?

 

[Tomk80]

All three images show bacteria with rounded-corner equant shapes. (different size, though)

Yeah, because animals have all are 90 degree right angles. Oh shoot, they don't.

 

[Assyrian]

I wonder how much of the perceived variation in the OP is a question of scale. To us bacteria look pretty similar and animals show wonderful variety. Yet to an e-coli we probably look pretty much the same as a cow. On the other hand our immune system learns to recognise some bug and deal with it, then it undergoes a simple little mutation and changes sugar or protein on the outside and suddenly our immune system is all 'hello, who are you, would you like to come in for coffee'.

 

[Split Rock]

We are in charge of them. If we don't like them, we can get rid of them. But they could not do the same. So, we (rare life) are "better" then the major forms (abundant) of lives on the earth.

Wow.. how wrong can one be concerning bacteria? We cannot wipe them out, anymore than we can wipe out roaches. Actually Tomk80 was wrong, smallpox is caused by a virus, not a bacterium. So, there is not even one bacterial pathogen we have eliminated, despite the obvious incentive to do so.

 

[Tomk80]

Wow.. how wrong can one be concerning bacteria? We cannot wipe them out, anymore than we can wipe out roaches. Actually Tomk80 was wrong, smallpox is caused by a virus, not a bacterium. So, there is not even one bacterial pathogen we have eliminated, despite the obvious incentive to do so.

*hides in a dark corner out of shame*

 

[juvenissun]

Not necessarily. I said sigma factors could control morphology for all I know. I only know very few things they control (biochemical responses to extreme heat and various other stresses), so I can't tell you if they actually do morphology.

More to the point, the number of sigma factors wouldn't necessarily correlate with morphological variability even if they had something to do with morphology. Take Hox genes; arthropods have only one Hox cluster (containing 11 genes in the fruit fly), we vertebrates have four (total 39 Hox genes in mammals). Yet are we more diverse than arthropods? I couldn't confidently say that.

Morphology is a complex thing that emerges from networks of gene interactions. You can't just take one type of control gene and say "more X factors = more diversity".

OK. So we do not know why are bacteria showing much simpler morphology than trees/animals.

 

[juvenissun]

Depends on the disease and the individual. It's an arms race, not a steady state. And given our need to develop medication, our immune system is far from beating them pretty solid.

Sure we did. Otherwise, Homo Sapients (and all other animals) won't survive.

I think this is an example on the advantage of being a multi-cellular life. That is why eukaryote cells evolved (see the advantages), but bacteria does not. May be they are genetically more variable, but they used a wrong strategy in the course of evolution and never corrected themselves. So they are sort of "stupid".