I took this from a very informative marijuana site:
A variety of bacteria grow on damp marijuana. Many are deadly. Researchers
have found _Klebsiella pneumoniae_, _Enterobacter cloacae_ and _Streptococcus_
(group D) growing in government-supplied reefer. _Salmonella muenchen_ was
found in marijuana growing across the Midwest. Under anaerobic conditions
(i.e., damp marijuana stored in airtight containers), _Clostridium_ species
will rot pot; these are the famous boutlism bacteria.
In addition, a number of bacteria-like Actinomycetes have been identified in
confiscated ganja, including _Thermoactinomyces candidus_, _T. vulgaris_, and
_Micropolyspora faeni._ These bugs cause allergic reactions (sometimes
severe), as well as "Farmer's lung" disease.
EDIT: I posted info on bacteria rather than fungi. Heres the info on mold and fungi....
Fungi destroy more bud than bacteria and insects combined. Bacteria in
marijuana may be more dangerous to humans, but they are rare. Molds are
common, and can be nasty: Ramirez reports four policeman developing pulmonary
histoplasmosis after pulling up a 5,000-square-meter plot of marijuana in
Puerto Rico. Some fungi won't rot pot, but they will put you in the hospital.
Many fungi causing disease in plants die off after their host is harvested.
Exceptions include _Botrytis cinerea_ (the cause of gray mold) and _Alternaria
alternata_ (brown blight). After harvest, your competition becomes
_Aspergillus_, _Penicillium_, _Rhizopus_, and _Mucor_, the baddest actors on
the planet. Each genus causes disease under different conditions:
Ubiquitous _Aspergillus_ grows on anything from rocket fuel to astronauts. The
genus is millions of years old; while _Home sapiens_ may come and go,
_Aspergillus_ will remain. Westendorp first found an _Aspergillus_ species
attacking _Cannabis_ in 1854. More recently, Margolis & Clorfene describe a
mold that _increases_ potency in marijuana. Their "black weblike fungus"
sounds like an _Aspergillus_ species. _What_ species, I'd like to know....
Schwartz scraped _Aspergillus niger_ from the skull of a marijuana smoker
experiencing sinus headaches. I frequently encounter _A. niger_ growing in
ganja stored at room temperature. It does _not_ increase potency. Kagen also
reports _A. niger_ growing in moldy marijuana, along with two _even nastier_
Aspergilli: _A. fumigatus_ and _A. flavus._
Chusid et al. blame _A. fumigatus_ for causing near-fatal pneumonitis in a
17-year-old. They note the patient buried his marijuana underground for
"aging." No doubt the patient was looking for Margolis & Clorfene's fungus,
but _A. fumigatus_ found him instead. _A. flavus_, on the other hand, kills
slowly. It oozes carcinogenic metabolites called aflatoxins. Llewellyn &
O'Rear found aflatoxins contaminating Virginian marijuana.
So you see, smoking moldy weed is definitely not in your best interest, and can leave you with much more than a bad taste in your mouth.