I'm curious what the average and max speed is for bacteria with cilia
and for bacteria with flagella ... and how the size of the bacteria
affects how fast it can go.

I realize there are a ton of different bacteria, so I don't need exact
numbers ... an order of magnitude is fine.
For the size issue, I'm just curious if the larger the bacteria the
faster (or slower?) it can move ... or if there is some ideal "swimmer
size" for each movement type.

The speed of a single-celled animal is affected mostly by the cell's
physiology and its environment. Unicellular organisms may swim or
crawl through their environments, depending on what appendages the
organism has for locomotion. Due to a cell's small size and
fluid-filled environment, the viscosity of the organism's surroundings
produces the greatest effect on its movement, rather than inertial
forces that larger organisms would encounter.

The speeds of single-celled animals vary greatly along with the
special locomotive structures that each cell has. Cells that glide
over solid surfaces can move at speeds ranging from 0.3 to 11.1 µm/s.
Flagellated cells can swim at speeds from 20 to 200 µm/s. Ciliated
cells can push themselves to speeds as high as 400 to 2000 µm/s.

Quoted from:
http://hypertextbook.com/facts/2000/RossKrupnik.shtml

The Reynolds number of an organism determines how easily viscous
forces affect the organism's motion.  Appearently, the Reynolds number
is a concept that useful for a broad spectrum of applications.

Information on Osborne Reynolds:
http://www.eng.man.ac.uk/historic/reynolds/oreynB.htm

Reynolds Number (Re) is a dimensionless ratio: inertial forces/viscous forces
more precise formula:
  ((body size)(fluid speed))/(kinematic viscosity)

Engineers worrying about problems of waterflow tend to use
Reynolds Number as well.

Since single-celled organisms are very small... the exist under very
low Reynolds numbers.  And as shown by the following website,
existence and transport with low Reynolds numbers is often
counter-intuitive.

http://66.102.7.104/search?q=cache:s6h7aWJ8FWUJ:brodylab.eng.uci.edu/~jpbrody/reynolds/lowpurcell.html+cilia+speed+reynolds&hl=en

Unfortunately I couldn't find anything on the "ideal" size of a
bacterium.  However, from what I've read, I would infer that ideal
size would depend upon environmental fluid viscosity and locomotive
type (cilia or flagella).

Basics on Cilia and Flagella:
http://biology.about.com/library/weekly/aa052500a.htm

Cilia and Flagella Movies
http://216.239.57.104/search?q=cache:qAAXmCOphqcJ:fybio.bio.usyd.edu.au/vle/L1/ResourceCentre/CAL/MicroConcepts/MDivSize.html+%22cell+size%22+flagellum+cilia&hl=en

Hope this helps :)
--Rcubed

Two websites didn't work right.

Life at Low Reynolds number
http://brodylab.eng.uci.edu/~jpbrody/reynolds/lowpurcell.html

Bacteria Movies
http://fybio.bio.usyd.edu.au/vle/L1/ResourceCentre/CAL/MicroConcepts/MDivSize.html#Movement

I'm amazed at the article written by Purcell.  I had to buy his E&M
textbook for school and he doesn't sound anything like that.  I'm also
amazed that was actually published in a journal ... such an incredibly
informal tone.

Anyway, thanks for the microbe speeds.
What's amazing is that it sounds like even a fairly slow river ... the
microbes can't swim upstream.  Strange.

I don't fully understand the Reynold's number, so can someone let me
know if the following is correct?  The Reynold's number seems to be
for making a comment that objects with the same Reynold's number have
similar motions (same motion just at different scales).

So, if an object trying to move faster, the velocity increases so it's
Reynold's number increases. At some point the bacteria can't move any
faster (depends on its locomotive type and size).

A larger bacteria of the same locomotive type is roughly just the
"same object on a larger scale" ... and if it speeds up until it's at
max speed, it's at a constant velocity limited by viscosity (just like
the smaller microbe at max speed, so it's similar motion at a
sifferent scale). So in this situation the Reynolds numbers should
match.

The reynolds number = length*velocity/(kinematic viscosity).  So to
keep a constant reynolds number, the velocity is inversely
proportional to the length scale.

So the larger the slower?

I guess a MUCH simpler way of looking at it is, if the cilia are what
"row" the microbe along, then the larger the surface area to volume
ratio (ie power to weight ratio) ... the faster it can move.  The
smaller the microbe, the larger the surface area to volume.

I guess that makes sense at some level.  It's still bizarre though as
I somehow expected size to help.

Thanks for your help.