Rhodococcus erythropolis strain PR4 has been isolated as an alkane-degrading bacterium. The strain harbours one linear plasmid, pREL1 (271 577 bp) and two circular plasmids, pREC1 (104 014 bp) and pREC2 (3637 bp), all with some sequence similarities to other Rhodococcus plasmids. For pREL1, pREC1 and pREC2, 298, 102 and 3 open reading frames, respectively, were predicted. Linear plasmid pREL1 has several regions homologous to plasmid pBD2 found in R. erythropolis BD2. Sequence analysis of pREL1 and pBD2 identified common metal-resistance genes on both, but pREL1 also encodes alkane-degradation genes not found on pBD2, with enzyme constituents some of which are quite different from those of other organisms. The alkane hydroxylase consisted of a cytochrome P450 monooxygenase, a 2Fe-2S ferredoxin, and a ferredoxin reductase. The ferredoxin reductase amino acid sequence resembles the AlkT (rubredoxin reductase) sequence. A zinc-containing alcohol dehydrogenase further oxydizes alkanols, alkane oxidation products catalysed by alkane hydroxylase. Of the circular plasmids, the pREC1 sequence is partially similar to the sequence of pREAT701, the virulence plasmid found in Rhodococcus equi. pREC1 has no pREAT701 virulence genes and encodes genes for beta-oxidation of fatty acids. Thus, joint actions of enzymes encoded by pREL1 and pREC1 may enable efficient mineralization of alkanes.
Acute-and convalescent-phase sera from patients with dengue (DEN) hemorrhagic fever (DHF) and Japanese encephalitis (JE) that contained pre-existing flavivirus antibodies were tested for cross-reacting antibodies to DEN, JE and yellow fever (YF) viruses by a neutralization (N) test . A fourfold or greater rise in N antibody titer in the convalescent-phase was considered significant . Of 39 DHF cases, obtained at Chiang Mai University Hospital, Thailand, 15 (38.5%) showed a rise in DEN antibody titer, while another 15 (38.5%) showed a significant rise in both DEN and JE N antibody titers. On the other hand, eight (61.5%) of 13 JE cases obtained at the same Hospital , showed a significant rise in JE antibody titer, while two (15.4%) showed a significant rise in both DEN and JE antibody titers. Sucrose gradient centrifugation and fractionation of these two crossreactive JE sera revealed that IgM class antibody was specific for JE , while IgG class antibody was cross-reactive. Of three JE cases with pre-existing YF antibody obtained in Okinawa , Japan, two showed a significant rise in YF and JE antibodies. Both IgM and IgG class antibodies to YF virus were elevated. These results indicate that the cross-reactivity among flaviviruses in different subgroups (complexes), was observed quite often, even by the N test , in sequential flavivirus infection.Key words: Flaviviruses, Sequential infections, Cross-neutralization testThere are more than 60 flaviviruses , including Japanese encephalitis (JE), dengue (DEN) and yellow fever (YF) viruses, and contain crossreactive antigens which make serodiagnosis difficult (11 for review). This is especially true in the regions where two or more flaviviruses are prevalent . Among the serological tests, the neutralization (N) test is considered to be more specific than complement-fixation (CF), hemagglutination-inhibition (HI) and enzyme-linked immunosorbent assay (ELISA) (16 for review). On the basis of close relationship in cross-neutralization tests using hyperimmune polyclonal antisera, flaviviruses are divided into at least eight antigenic subgroups (complexes), where JE and DEN viruses are classified into different subgroups, while YF virus remains unassigned (I).In Japan, only one flavivirus , i.e. JE virus, has been prevailing and HI test or ELISA has been employed for serodiagnosis without problems. While in the Southeast Asian countries such as Thailand and Vietnam, JE and DEN viruses have been coexisting and the outbreaks caused by these viruses have taken place simultaneously in the rainy season (6). It has been reported that in the secondary DEN virus infection, the serotype of the causative virus of the recent infection could not be identified by N test because of the cross-reactions . It was possible only by virus isolation or detection of specific viral genomic sequence (13). Secondary DEN infection in previously immune individuals with another serotype of DEN virus elicits broadly
This presentation should not be reported as representing the views of the IMF. The views expressed in this presentation are those of the presenters and do not necessarily represent those of the IMF or IMF policy. It describes research in progress by the presenters and are presented to elicit comments and further debate.
To enzymatically synthesize active metabolites of vitamin D3, we screened about 500 bacterial strains and 450 fungal strains, of which 12 strains were able to convert vitamin D3 to 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3] via 25-hydroxyvitamin D3 [25(OH)D3]. The conversion activity was only detected in strains belonging to the genus Amycolata among all the organisms tested. A preparative-scale conversion of vitamin D3 to 25(OH)D3 and 1 alpha,25(OH)2D3 in a 200-1 tank fermentor using A. autotrophica FERM BP-1573 was accomplished, yielding 8.3 mg 25(OH)D3/l culture and 0.17 mg 1 alpha,25(OH)2D3/l culture. A related compound, vitamin D2, could be also converted to 25-hydroxyvitamin D2 and 1 alpha,25-dihydroxyvitamin D2 using the same strain. The cytochrome P-450 of FERM BP-1573 was detected by reduced CO difference spectra in whole-cell suspensions. Vitamin D3 in the culture induced cytochrome P-450 and the conversion activity simultaneously, suggesting that the hydroxylation at C-25 of vitamin D3 and at C-1 of 25(OH)D3 originates from cytochrome P-450.
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