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Rhodococcus (opacus) erythropolis HL PM-1 grows on 2,4,6-trinitrophenol or 2,4-dinitrophenol (2,4-DNP) as a sole nitrogen source. The NADPH-dependent F 420 reductase (NDFR; encoded by npdG) and the hydride transferase II (HTII; encoded by npdI) of the strain were previously shown to convert both nitrophenols to their respective hydride Meisenheimer complexes. In the present study, npdG and npdI were amplified from six 2,4-DNP degrading Rhodococcus spp. The genes showed sequence similarities of 86 to 99% to the respective npd genes of strain HL PM-1. Heterologous expression of the npdG and npdI genes showed that they were involved in 2,4-DNP degradation. Sequence analyses of both the NDFRs and the HTIIs revealed conserved domains which may be involved in binding of NADPH or F 420 . Phylogenetic analyses of the NDFRs showed that they represent a new group in the family of F 420 -dependent NADPH reductases. Phylogenetic analyses of the HTIIs revealed that they form an additional group in the family of F 420 -dependent glucose-6-phosphate dehydrogenases and F 420 -dependent N 5 ,N 10 -methylenetetrahydromethanopterin reductases. Thus, the NDFRs and the HTIIs may each represent a novel group of F 420 -dependent enzymes involved in catabolism.

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A 4-nitrophenol (4-NP)-degrading bacterium was isolated from activated sludge and identified as a Rhodococcus sp. This bacterium, designated as strain PN1, could utilize 4-NP as a sole carbon, nitrogen and energy source. Degradation tests of 4-NP using cell suspensions of strain PN1 revealed that the degradation was induced by 4-NP and that 4-nitrocatechol (4-NC) was one of the metabolites. A gene library was constructed from the total DNA of strain PN1 and introduced into Rhodococcus rhodochrous ATCC 12674. Two recombinant strains showed 4-NP hydroxylase activity, and a 9.1-kb DNA fragment encoding the activity was isolated from one of the strains. In addition, a 2.4-kb smaller fragment expressing the activity was subcloned from the 9.1-kb fragment and sequenced. The sequence analysis showed that the fragment encodes a two-component 4-NP hydroxylase, the predicted amino acid sequence of which exhibits significant similarity to those of phenol hydroxylases and 4-hydroxyphenylacetate 3-hydroxylases belonging to the two-component flavin diffusible monooxygenase (TC-FDM) family proposed by Galán et al. (J. Bacteriol., 182, 627-636, 2000).

Innervation of the lateral line canal system in seven batoid species (representing seven families in three orders) provided a reliable basis for the identification of each canal element. Previous topographic definitions of the canal elements have failed to recognize homologies within batoids for the scapular and hyomandibular canals. The former is innervated by the posterior lateral line nerve and the latter is innervated by an external mandibular branch of the anterior lateral line nerve. This indicates that the scapular canal is represented only by the scapular loop in Myliobatoidei.