Recombinant DNA techniques. Bulk chromosomal DNA
was isolated from a mid-log-phase culture of R. albus 8 by
the procedure of Marmur (23), modified by the addition of
mutanolysin (lysozyme is ineffective against Ruminococcus
cell walls), and was scaled up to yield appropriate amounts
of chromosomal DNA. XDASH (Stratagene Cloning Systems)
was used as specified by the supplier. Recombinant
phage X DNA was isolated from phage lysates by the
procedures of Crossberger (16). Restriction endonucleases
and T4 ligase were obtained from Bethesda Research Laboratories,
Inc., Gaithersburg, Md., and used as recommended
by the supplier.