4/23/97

Good morning,



I have a colleague who would like to know if there is a way to

deside if

bacteria in activated sludge are gram-positive or gram-negative.

Fresh

samples were mixed with glycerol and frozen, thawed and prepared

for SEM

and TEM ( GA, OsO4, epoxy). There are no obvious signs of either

gram-pos

or neg. Is there any stain for sections?

Fresh samples are no longer available.



TIA



Gunnel Karlsson



^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Gunnel Karlsson E-mail

Gunnel.Karlsson@oorg2.lth.se

Biomicroscopy Unit Tel +46 222 8229

Inorganic Chemistry 2 Fax +46 222 4012

Box 124

S-221 00 LUND, Sweden

Gram negative can readily be distinguished from gram positive

bacteria by

examination of the structure of the cell wall by TEM. Check any

good

general bacteriology book for figures. The outermost layers

("wall") of

gram negs show what appear to be two unit membranes with a thin

(usually

dense) amorphous layer between. This outermost membrane

(containing

lipopolysaccharide -> common in G- but extremely rare in G+) is

most often

undulated, giving the appearance of a ruffled surface by SEM.

Gram

positives, on the other hand, have a single cell membrane with a

thick

(usually electron-light) wall exterior to the membrane. The wall

is

composed of peptidoglycan and lacks LPS or lipopolysaccharide. If

you need

more info or require a specific reference, contact me.







#################################################################

###

John J. Bozzola, Ph.D., Director

Center for Electron Microscopy

Neckers Building, Room 146 - B Wing

Southern Illinois University

Carbondale, IL 62901-4402

U.S.A.

Phone: 618-453-3730

Fax: 618-453-2665

Email: bozzola@siu.edu

Web: http://www.siu.edu/departments/shops/cem.html

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