CHANGES IN BACTERIA RECOVERABLE FROM SUBSURFACE VOLCANIC ROCK SAMPLESDURING STORAGE AT 4-DEGREES-C

The abundance of viable microorganisms recovered from deep subsurface volcanic rock samples increased after rock perturbation and storage fo r 1 week at 4 degrees C, while the diversity and evenness of recoverab le heterotrophic bacterial communities generally decreased. One sample of each morphologically distinct colony type, recovered both before a nd after storage of U12n rock samples, was purified and characterized by fatty acid methyl ester (MIDI) and API rapid NFT strips. As determi ned by MIDI cluster analysis, the composition of the recoverable micro bial communities changed with storage of rock samples; some groups of organisms were recovered only before, only after, or at both sample ti mes. In general, the isolates recovered only after storage of rock sam ples had a greater ability to utilize the carbohydrates included in AP I test strips and had faster generation times than isolates recovered only on initial plating. The nutritional versatility and faster growth rates of organisms recovered in higher proportions after sample stora ge provide evidence that some microbial community changes may be due t o the proliferation of a few bacterial types. However, because some ne w genera are recovered only after storage, the possibility also exists that dormant bacterial types are resuscitated during sample perturbat ion and storage.