The Relation of Microörganisms to the Development and Longevity of Flies
R. W. Glaser
From the Department of Animal Pathology, of The Rockefeller Institute for Medical Research, Princeton, New Jersey
1. The growing or larval stages of flies are dependent uponcertain accessory growth factors which must be ingested withthe food.
2. These accessory growth factors are obtained bythe larvaefrom bacteria or yeasts, as well as from higher plantand animaltissues.
3. When rearing flies on media sterilizedat high temperatures,the necessary growth factors for the larvaeare destroyed, butcan be replaced by contaminating the mediawith living bacteriaor yeasts, by adding large quantities ofdead bacteria or yeastskilled at low heat, or by adding freshsterile animal tissueextracts or fresh, sterile plant juices.
4. Non-pathogenic bacteria, when ingested by adult flies shortentheir life span and reduce the number of ovipositions.
5.Microörganisms and their activities are not absolutelyessential to the normal growth, development, and longevity ofthe flies investigated.
6. Microörganisms are presentin wild flies, especiallyin the larvae, because owing to theirhabits the ingestion ofbacteria, yeasts, fungi, etc., cannotbe avoided.
7. Microörganisms may be one of the principalsources forthe accessory growth factors of some larval fliesfound breedingin certain types of media in a state of nature,but this assumptionmust not be regarded as a proved fact.