Sunday, January 20, 2013

What is cell life?

Welcome to the cell biology blog. This blog is for students in the cell biology course at The Master's College, but anyone is free to join. My name is Dr Francis and I teach the cell biology course. Please feel free to contact me at jfrancis@masters.edu if you have questions about this blog.

What are cells? Cells are often distinguished from viruses, but recent discoveries of some very large viruses suggest that this distinction is becoming more and more fuzzy.


Also, is there such a thing as unicellular life? Can cells and do some organisms exist as single cells? Well I might be going out on a limb but I do not believe that unicellular life exists. That is certainly a statement that is subject to a lot of interpretation. Let me explain.

First, single cells do exist, and some appear to lead independent lives, for instance creatures we call microbes like bacteria or paramecium. So what then does the term unicellular mean? It is a term used to distinguish free living independent cells from those which live in tissues, or the multicellular condition. Cells which live in this multicellular state live in close contact with other cells. But I would argue that all cells live in close contact with other cells.
 
So how likely is it that you are going to find microbes living alone, in a true unicellular state. Take a pinch of soil; you will find thousands of creatures living there, many interacting with each other. Consider an amoeba or paramecium or other pond organism. How many of these creatures do you know who live in their own private pond?!
 
But really, lets get down to the nitty gritty, could you not isolate a single bacterium and give it a nice petri dish with lots of nutrients in the corner of your room? But wait a minute, about every 30 minutes, this guy will generate his own friends, within a few hours a full grown microbial party will be in force. I am wondering just how easy it is to isolate a single living bacterium. How would you do it?

I challenge the microbiology students every year and tell them I will give them an A in the lab course if they can isolate and stain a single bacterium on a single microscope slide. What would you have to do to accomplish this task? ( I might give some credit just for a protocol for how you would do this).

Lets face it. Life is multicellular at every level. But wait. What about those pond organisms? they seem independent. More and more studies are showing that most of these critters carry bacteria around. There is even one strain that lives with a bacterium in its macronucleus. Why in the world would you want to carry a bacterium in your macronucleus? I have asked a lot of people, and no one has given me a satisfactory answer. I have gotten some weird looks ….as if the person is thinking, what the heck is a macronucleus and why do I care?

A lot of single celled pond organisms eat bacteria or algae. But there is one pond organism Paramecium bursarium which eats algae and bacteria but also knows how to ingest some algae and not digest them; instead it keeps them as energy harvesting slaves! Whoa! How does it know to eat some critters and digest them and eat other critters an not digest them? Remember this is a small creature with no brain and no nervous system.


So the questions for the blog today are:

1 Investigate the Mimi virus and explain how it is like cells but also different from cells. Is this a true virus in your opinion?

2 Mimi virus is infected with viruses.  What are these viruses and what  could they being doing inside Mimi virus?

3 What is a macronucleus and why would you want to live there? cheap rent? cozy?

4 How would you isolate a single bacterial cell on a microscope slide?

5 How can Paramecium eat algae but not digest it?

6 What is the advantage to being multicellular?

Blog responses are due Feb 4.



5 What is significant about the concept that all living creatures are multicellular?