Transgenic bacteria producing pyrroloquinoline quinone, a known cofactor for dehydrogenases and an inducer of a periplasmic protein kinase activity, show resistance to both oxidative stress and protection from nonoxidative effects of radiation and DNA-damaging agents. Deinococcus radiodurans R1 encodes an active pyrroloquinoline quinone synthase, and constitutive synthesis of pyrroloquinoline quinone occurred in wildtype bacteria. Disruption of a genomic copy of pqqE resulted in cells that lacked this cofactor. The mutant showed a nearly 3-log decrease in ␥ radiation resistance and a 2-log decrease in mitomycin C tolerance compared to wild-type cells. The mutant cells did not show sensitivity to UVC radiation. Expression of pyrroloquinoline quinone synthase in trans showed that there was functional complementation of ␥ resistance and mitomycin C tolerance in the pqqE mutant. The sensitivity to ␥ radiation was due to impairment or slow kinetics of DNA double strand break repair. Low levels of 32 P incorporation were observed in total soluble proteins of mutant cells compared to the wild type. The results suggest that pyrroloquinoline quinone has a regulatory role as a cofactor for dehydrogenases and an inducer of selected protein kinase activity in radiation resistance and DNA strand break repair in a radioresistant bacterium.Pyrroloquinoline quinone (PQQ) has been shown to be a redox cofactor for periplasmic as well as cytosolic dehydrogenases, contributing to the mineral phosphate solubilization phenotype in bacteria (11). This compound has been reported to act as an antioxidant in vitro (33), in animal systems (13), and in bacterial systems (18) in vivo and as a member of the B group vitamins (16). He and coworkers (13) have shown that the antioxidant nature of PQQ is concentration dependent. Higher concentrations of PQQ induce oxidative stress for mitochondrial activity in rats, which leads to both apoptotic and necrotic cell death. Further studies indicated that the necrotic cell death could be selectively inhibited in the presence of antioxidants, while apoptotic cell death continued by a stillunknown mechanism. Further, a possible role for PQQ as an inducer for proteins kinases involved in distinctly different metabolic and physiological processes has been suggested (20).Deinococcus radiodurans R1, a gram-positive bacterium, exhibits extraordinary tolerance to various abiotic stresses, including radiation, desiccation, and other DNA-damaging factors (3). DNA double strand break repair in D. radiodurans R1 follows biphasic kinetics (8). Phase I is RecA independent and involves an extended synthesis-dependent strand annealing mechanism for reassembly of the fragmented genome (42), while phase II involves RecA-dependent slow crossover events (9). The extreme phenotypes of this bacterium are believed to be due to the presence of an efficient DNA strand break repair mechanism (1, 31) and strong oxidative stress tolerance (27). A comparison of the genome sequence of D. radiodurans R1 (41) with the genome sequenc...

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Camptothecin (CPT), the derivatives of which are used clinically for the treatment of metastatic colon cancer, is isolated from intact plants that can be subjected to environmental fluctuations. In vitro cultures may be an alternate and continuous source for year-round production of CPT. Since CPT production by undifferentiated cell cultures is low, differentiated tissues such as root cultures may be a viable alternate source for CPT production. Hairy roots were induced in Ophiorriza rugosa, a source of CPT, using Agrobacterium rhizogenes strain LBA9402. The hairy roots, when cultured in light, showed spontaneous regeneration of shoots. Analysis of CPT levels in the hairy roots and in vitro-grown transformed shoots revealed 0.009% d.w. and 0.012% d.w., respectively.

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