14.18 “Symbiosis Between Termites and Their Intestinal
Protozoa” by Lemuel Cleveland, 1923
Lemuel Roscoe Cleveland was working at Johns Hopkins University in Baltimore,
Maryland, studying the relationship between termites and their intestinal protozoa.
He examined the intestinal contents of termites in a museum collection and determined that whenever wood was present so were protozoa, and whenever protozoa
were present so was wood. Thus, there was a clear positive correlation between a
wood-feeding habit and the presence of protozoa. Cleveland discovered through
experimentation that the relationship between wood-feeding termites and their
intestinal protozoa was temperature labile. Incubation of termites for 24 h at 36
C
resulted in death of the harbored intestinal protozoa. The incubated termites survived
this thermal treatment, and Cleveland described those surviving termites as being
defaunated. The defaunated termites subsequently were able to ingest their normal
diet of wood but unable to derive sustenance from ingesting that wood, and the
termites instead seemed to die from starvation. Feeding either fungus-digested
cellulose or humus to the defaunated termites allowed the termites to survive.
Permitting defaunated termites to have coresidence with unincubated termites
resulted in the defaunated termites becoming reinoculated with protozoa, a process
which Cleveland described as being a reinfection of the termites. Following
coresidence, the defaunated termites with their population of reacquired intestinal
protozoa were able to survive as normal on a diet of either wood or cellulose.
Starving termites by denying them wood resulted in a change of the intestinal
protozoa population, those protozoa which ingested wood were eliminated from
the intestine but the non-wood-ingesting protozoa remained abundant. The starved
termites subsequently could ingest wood but lacked ability to digest that wood.
Cleveland surmized that the wood-ingesting protozoa possibly split the cellulose
into cellobiose, the cellobiose into glucose, and then created glycogen from the
glucose. He presumed that the termites were obtaining sustenance from the products
generated by those protozoa.
14.19 “Strain Variations and Host Specificity
of the Root-Nodule Bacteria of the Pea Group” by
George Helz, Ira Lawrence Baldwin, and Edwin
Broun Fred, 1927
George E. Helz, Ira Lawrence Baldwin, and Edwin Broun Fred (1927), working at
the Department of Agricultural Bacteriology, University of Wisconsin, tested seventeen different strains of bacteria which induce formation of root nodules in legume
crops. Their goal was to increase the harvest yields of garden pea (Pisum sativum)
although their selection of studied plants was wider in scope than peas alone, with
inclusion of broad bean (Vicia faba), hairy vetch (Vicia villosa), lentil (Lens
esculenta), and sweet pea (Lathyrus odoratus).
236
C. J. Hurst
Protozoa” by Lemuel Cleveland, 1923
Lemuel Roscoe Cleveland was working at Johns Hopkins University in Baltimore,
Maryland, studying the relationship between termites and their intestinal protozoa.
He examined the intestinal contents of termites in a museum collection and determined that whenever wood was present so were protozoa, and whenever protozoa
were present so was wood. Thus, there was a clear positive correlation between a
wood-feeding habit and the presence of protozoa. Cleveland discovered through
experimentation that the relationship between wood-feeding termites and their
intestinal protozoa was temperature labile. Incubation of termites for 24 h at 36
C
resulted in death of the harbored intestinal protozoa. The incubated termites survived
this thermal treatment, and Cleveland described those surviving termites as being
defaunated. The defaunated termites subsequently were able to ingest their normal
diet of wood but unable to derive sustenance from ingesting that wood, and the
termites instead seemed to die from starvation. Feeding either fungus-digested
cellulose or humus to the defaunated termites allowed the termites to survive.
Permitting defaunated termites to have coresidence with unincubated termites
resulted in the defaunated termites becoming reinoculated with protozoa, a process
which Cleveland described as being a reinfection of the termites. Following
coresidence, the defaunated termites with their population of reacquired intestinal
protozoa were able to survive as normal on a diet of either wood or cellulose.
Starving termites by denying them wood resulted in a change of the intestinal
protozoa population, those protozoa which ingested wood were eliminated from
the intestine but the non-wood-ingesting protozoa remained abundant. The starved
termites subsequently could ingest wood but lacked ability to digest that wood.
Cleveland surmized that the wood-ingesting protozoa possibly split the cellulose
into cellobiose, the cellobiose into glucose, and then created glycogen from the
glucose. He presumed that the termites were obtaining sustenance from the products
generated by those protozoa.
14.19 “Strain Variations and Host Specificity
of the Root-Nodule Bacteria of the Pea Group” by
George Helz, Ira Lawrence Baldwin, and Edwin
Broun Fred, 1927
George E. Helz, Ira Lawrence Baldwin, and Edwin Broun Fred (1927), working at
the Department of Agricultural Bacteriology, University of Wisconsin, tested seventeen different strains of bacteria which induce formation of root nodules in legume
crops. Their goal was to increase the harvest yields of garden pea (Pisum sativum)
although their selection of studied plants was wider in scope than peas alone, with
inclusion of broad bean (Vicia faba), hairy vetch (Vicia villosa), lentil (Lens
esculenta), and sweet pea (Lathyrus odoratus).
236
C. J. Hurst