| Abstract |
- Bacteria of the genus Klebsiella have been found to be
associated with redwood water storage reservoirs, redwood
chips, and liquid expressed from within living redwood. A
1,000 gallon experimental redwood reservoir was employed to
determine how to control the presence of Klebsiella and
Enterobacter in drinking water stored in these tanks. Over
a twenty month period of operation, these coliforms were
not detected in tank water. Control of Klebsiella and
Enterobacter was dependent on three factors: maintenance of
a free chlorine residual of 0.2-0.4 ppm in the tank water,
maximum retention times of four to seven days, and the use
of a separate overhead inlet water pipe. Klebsiella
multiplied to 10⁶ per ml in dechlorinated water samples from
the experimental tank, utilizing nutrients leached from the
redwood. The predominant metabolizable carbon sources in
aqueous extracts of redwood are cyclitol compounds, of which myo-inositol is the parent compound. Pinitol and sequoyitol,
two other cyclitols, are also encountered in redwood. 100%,
97%, and 68% of the combined Klebsiella isolates from
clinical and environmental origins fermented inositol,
sequoyitol, and pinitol, respectively. These compounds can
also be used as a sole source of carbon and energy by
Klebsiella. Similar results were obtained with Enterobacter
isolates, but most other enteric bacteria tested could not
metabolize cyclitols. Strains of Klebsiella multiplied to
levels exceeding 10⁵/ml in aqueous extracts of non-sterile
redwood within 6 days. Most other enteric bacteria did not
grow in these extracts. Cyclitol metabolism correlated well
with the ability to multiply in redwood extract in the
presence of cyclitol-negative indigenous bacteria. Other
experiments were conducted with three small redwood tanks
in order to assess the effects of chlorine residuals,
retention times, and cyclitol concentrations in redwood
tank Water on coliforms and on Klebsiella. As chlorine
residuals were increased, coliform and total bacterial
counts decreased. Longer retention times resulted in the
accumulation of cyclitol compounds and a decrease in
chlorine residuals. A decrease in cyclitol concentration
was found to correlate with a drop in coliform and
Klebsiella densities. No cyclitol degradation by
indigenous coliforms was observed in water taken from the tanks, which partially explained why water flow is required
to completely remove cyclitols from a redwood tank. In
another study, gas chromatographic analysis was employed to
demonstrate in situ cyclitol utilization in redwood extracts
by isolates of Klebsiella, Enterobacter, and other gramnegative
bacteria. In aqueous redwood extracts, all of the
Klebsiella tested reached densities exceeding 5.0x10⁶ cells/ml within 4 days and all utilized pinitol and
sequoyitol, as did Enterobacter. Other enteric bacteria did
not utilize cyclitols in this extract. A defined minimal
medium, containing the carbohydrates and cyclitols in redwood,
was used to determine which carbon sources are preferentially
utilized by Klebsielleae and other bacteria. It was found
that D-glucose and L-arabinose were consumed by Klebsiella
before the cyclitols were utilized. Pinitol utilization
proceeded more slowly than that of sequoyitol and myoinositol.
Cyclitol utilization in the defined medium was
also observed for strains of Yersinia, Erwinia, and
Salmonella. E. coli isolates did not utilize cyclitols.
The ability to use cyclitols as a carbon source can explain
the presence of Klebsiella and Enterobacter in redwood water
storage reservoirs and in redwood lumber. This ability may
also be related to their presence and growth in other
botanical material containing cyclitol compounds. Other
experiments demonstrated the utilization of myo-inositol hexaphosphate (phytic acid) by Klebsielleae, and the
transfer of antibiotic resistance between strains of
Klebsiella in aqueous extracts of redwood sawdust with cell
densities of Klebsiella likely to occur in nature.
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