Questions about individuals in relation to colonies - Questions about individuals in relation to colonies (Jan/08/2010 )
Hello!
First of all, I am nothing short of a complete novice when it comes to the subject of microscopic life. I only recently took it upon myself to learn everything I can about the subject, and in the natural course of my research a number of questions have popped up. I appeal to the knowledge and experience of other people visiting this forum to help me clear up some confusion that I have about a few things. Any effort to accomplish this will be greatly appreciated.
In researching Cyanobacteria, I keep reading about it existing in unicellular forms and colonial/ filamentous forms. Take Oscillatoria for example- in all of the images I see of it, it is a single green strand, usually clumped together with other green strands. What I"m wondering is if each strand is a single individual, or if the rectangular cells that make up the strand are themselves individual organisms making up a colonial strand. I guess I'm hazy on what constitutes an individual in this sense. Or with Nostoc, there are the grape-looking colonies, and inside are the beaded string filaments. Are each of the beads a separate organism, or is the string as a whole just one living thing? The lines seem to be blurred when it comes to free-living individuals and colonies.
I recently encountered the same confusion with Fungi. Since all the text I read referred to fungi as colonies, I assumed that each hypha is a separate individual, and they all link and work together as a colony. I now understand that it's an isolated mycelium which constitutes a single fungal organism, with the mushrooms being its various appendages for reproduction (I HOPE I'm correct by assuming this). So why is the term 'colony' applied to fungi?
Again, I thank you for bearing with me and can't wait to hear your responses!
Its not always easy to define a "individual" or "colony".
Each bead can can break off and start another "fungus", but when they are still togheter they all form 1 indivual ... well thats how I see it, they co-operatre, or live together.
But you should read a basic textbook on microbiology.
Do you have any such book?
with humans its easy: one human one indivudual, with bacteria or fungi its another case..
Exp: CFU: colony forming units, they come from 1 bacteria however 1 colony are more bacteria together but still all those bacteria come from the same individual (same bacterium cell)...
So with bacteria is still possible to say: each bacterium is one indivudial, but with fungi its not always that easy. All the beads togheter: 1 indivual, 1 bead breaks off and this beads forms a new fungus.
What is the smallest unit capable of reproducing? This is what I would call an individual.
Though I'm not a fungi guy, I would consider each of the "beads" individuals, and a string of them a colony. Just as I would consider a bacterial colony a group of loosely associated individuals, I would consider a filament a group of not-so-loosely associated individuals.
Not sure what the prevailing opinion is though...
HomeBrew on Jan 22 2010, 03:49 AM said:
Not sure what the prevailing opinion is though...
this is a very difficult question....and I think the answer cannot be clearly given....esp. for fungi. Some can reproduce asexually with conida and sexually with spores fromed in the fruiting bodies. So the reproductive units are easiely defiend. Nevertheless some can form clamydospores, sklerotia etc which is are just modified cells from the mycelium that help to survive difficult conditions....not to difficult as well. But when it comes to the mycelium in soil: like pito already mentioned: if you dig a hole to seperate two parts of the mycelium they will still be able to survive individually (in contrast to earthworms
) and given enough time and environmential pressure they can develope different properties (like e.g. carbon source they use)....so here we are touching philosophy I think 
@ Stephanoceros: find a basic textbook on microbiology like pito suggested. And be careful as a lot scientists and scientific writers (esp. on the internet) are not very careful in using terms like colony, species, isolate, organism etc.