Chapter 11 Lab Exercises
Section 12 Henrici's Microbial Fishing Technique
Page 3 Student
Copyright © Alfred B. Cunningham, John E. Lennox, and Rockford J. Ross, Eds. 2001-2010
Henrici’s Microbial Fishing
Technique1
Introduction
“Some time ago an aquarium in my
laboratory developed on its walls a growth of algae. Some
microscope slides were placed in the aquarium in the
expectation that the algae would also grow on these and that
permanent preparations might be made showing the organisms in
situ. On removing and staining these slides after a week's
immersion, I was surprised to find, in addition to the algae, a
thin and uniform coating of bacteria of various forms, some of
unusual morphology”. … “It is quite evident
that for the most part the water bacteria are not free floating
organisms, but grow upon submerged surfaces; they are of the
benthos rather than the plankton”. Arthur T.
Henrici1.
These comments written in 1933 indicate, that long before the
term biofim was used2, Henrici understood the basics of biofilm
formation. Elsewhere in that same article Henrici showed that
he had an understanding of biofilms that sounds modern even by
contemporary standards.
This understanding included the facts that
1) the bacterial cells are actually growing on the slide
as confirmed by the presence of microcolonies,
2) they are firmly attached to the glass slide,
3) the cells are surrounded by a matrix (sheath of gum)
which holds the cells to the slide,
4) specimens from aquaria and lakes alike produced these
biofilms,
5) most bacteria are not in the water column but rather
are surface attached.Using techniques very much like those described by Henrici
it is possible to “fish” for bacteria, algae,
protozoa and microinvertebrates by placing clean glass
microscope slides in an aquatic environment such as aquaria,
lakes, streams, showers, the tanks of toilet bowls, and any
other site where there is a large or small body of water either
standing or flowing.
Supplies Needed
Quantity |
Description |
As Necessary |
18 gauge wire |
1 |
wire cutters and pliers and shears |
1 |
spine from a student report binder |
As Necessary |
rubber bands |
As Necessary |
microscope slides (or preprinted slides from Erie
Scientific or other distributer) |
As Necessary |
transparent tape or Parafilm® M |
Instructions:
Henrici placed microscope slides in
aquaria and lakes in order to harvest a variety of living,
surface-attached bacteria. This same approach can be employed
by students today.
With this device (Figure 1), single microscope slides can be
anchored in natural aquatic environments where biofilms might
form.
Permissions
Staff, Center for Biofilm Engineering, Montana State University, Bozeman
Figure 1. A micro-fishing frame for holding a
microscope slide in a stream or aquarium
Permissions
Staff, Center for Biofilm Engineering, Montana State University, Bozeman
Figure 2. Several slides can be sited together in a
device made from the plastic spine of a plastic binder,
usually used to hold student reports.
- The spine can be cut in half and about six clean
microscope slides can be inserted into the two halves thus
formed.
- The halves of the binder are held together by rubber
bands.
- In this way six slides can be sited as a unit.
- Individual slides can be removed at intervals and
examined for biofilm production.
Cells can be harvested from biofilms formed on microscope
slides by using the preprinted slides distributed by Erie
Scientific Company (20 Post Road, Portsmouth, NH). These slides
are printed with multiple clear zones separated by a highly
hydrophobic masking material. The number of wells can vary from
1 to 12 and the size of the wells range from 4 to 14 mm. By
scraping and harvesting the cells within a “well,”
cells are gathered within a known surface area (A =
πr
2).
Permissions
Permission pending, Erie
Scientific Company.
Figure 3. Preprinted slides distributed by Erie
Scientific Company.
A multiple well slide can also be used in a microbial
fishing exercise by masking all but one of the wells with
transparent tape or Parafilm® M prior to placing the slide
at its site. Then each day or at another selected interval, one
additional well can be exposed. At the end of the sampling
period each student has a sequence representing the growth of a
biofilm over a period of time all on one slide.
Permissions
Permission pending; ASM Microbe Library
Figure 4. Biofilm accumulation on a glass surface
The results, with a little luck, appear as in Figure 4, shown
from the ASM Microbe Library biofilm collection. This image is
of a mixed biofilm of
Pseudomonas aeruginosa,
P. fluorescens and
Klebsiella pneumoniae and was photographed under confocal
microscopy3. The various panels illustrate the accumulation of
a mixed biofilm on a glass surface at 72, 98, 122, 144, 165,
191, 220. 268 and 309 hours (reading from top left to bottom
right). Note the complex structure of biofilm clusters (dark
patches) and water channels and the sloughing event that
occurred between 268 and 309 hours.
REFERENCES
1Studies of Freshwater Bactria: I. A Direct
Microscopic Technique
Henrici, AT
Journal of Bacteriology 1933; 25:277-286
2How Bacteria Stick
Costerton JW, Geesey GG, Cheng K-J
Scientific American 1978; 238(1):86-95
3Flow induced vibrations, drag force, and
pressure drop in conduits covered with biofilm
Lewandowski Z, Stoodley P
1995. International IAWQ Conference Workshop on Biofilm
Structure, Growth, and Dynamics, 30 Aug. to 1 Sept.,
Noordwijkerhout, The Netherlands.
This material is based upon work supported by the National
Science Foundation under Grant No. 0618744, and in part by the
Waksman Foundation for Microbiology. Developed in collaboration
with Dr. John Lennox, Penn
State Altoona. Any opinions, findings, and conclusions or
recommendations expressed in this material are those of the
author(s) and do not necessarily reflect the views of the
National Science Foundation.
©2002-2008 Center for Biofilm Engineering, http://www.biofilm.montana.edu