GROWING GOURMET - Anto2ni.it

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THE SIX VECTORS OF CONTAMINATION
sterilized, for all practical purposes, the outside
of the vessel has not been. Contaminants
can be easily picked up by the hands of the person
handling the pressure cooker and
re-distributed to the immediate workstation.
All the more the reason one should disinfect
before beginning transfers.
5. The Inoculum: The inoculum is the tissue
that is being transferred, whether this
tissue is a part of a living mushroom, mycehum
from another petri dish, or spores.
Bacteria and molds can infect the mushroom
tissue and be carried with it every time a transfer
is made. Isolation of the inoculum from the
mushroom mycelium can be frustrating, for
many of these contaminant organisms grow
faster than the newly emerging mushroom
mycelium. Cultivators must constantly "run"
or transfer their mycelium away from these
rapidly developing competitors. Several techniques
can purify contaminated mycelium.
6. MCU's, Mobile Contamination Units:
Mobile Contamination Units are organisms
that carry and spread contaminants within the
laboratory. These living macro-organisms act
as vehicles spreading contaminants from one
site to another. They are especially damaging
to the laboratory environment as they are difficult
to isolate. Ants, flies, mites, and in this
author's case, small bipedal offspring (i. e.
children) all qualify as potential MCU's. Typically,
a MCU carries not one contaminant, but
several.
Mites are the most difficult of these MCU's
to control. Their minute size, their preference
for fungi (both molds and mushroom mycehum)
as food, and their penchant for travel,
make them a spawn manager's worst nightmare
come true. Once mite contamination
levels exceed 10%, the demise of the labora-
tory is only one generation away. The only solution,
after the fact, is to totally shut down the
laboratory. All cultures must be removed, including
petri dishes, spawn jars, etc. The
laboratory should then be thoroughly cleansed
several times. I use a 10% household bleach
solution. The floors, walls, and ceiling are
washed. Two buckets of bleach solution are
used—the first being the primary reservoir, the
second for rinsing out the debris collected in
the first wipe-down. The lab is locked tight for
each day after wash-down. By thoroughly
cleansing the lab three times in succession, the
problem of mites can be eliminated or subdued
to manageable levels. Mycelia are regenerated
from carefully selected stock cultures.
I have discovered "decontamination mats",
those that labs use at door entrances to remove
debris from footwear, are ideal for preventing
cross-contamination from mites and similarly
pernicious MCU's. Stacks of petri dishes are
placed on newly exposed sticky mats on a
laboratory shelf with several inches of space
separating them. These zones of isolation,
with culture dishes incubating upon a highly
adhesive surface, make the migration of mites
and other insects a most difficult endeavor. The
upper sheet is removed every few weeks to expose
a fresh, clean storage plane for new
cultures.
All of these vectors are universally affected
by one other variable: lime of Exposure. The
longer the exposure of any of the aforementioned
vectors of contamination, the more significant
their impact. Good laboratory technicians are
characterized not only by their speed and care,
but by their rhythm. Transfers are done in a
systematically repetitive fashion. Controlling
the time of exposure can have a drastic impact
on the quality of laboratory technique.
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