Rapid evolution of low-pathogenic H9N2 avian influenza viruses following poultry vaccination programmes.

To investigate whether currently circulating H9N2 avian influenza viruses (AIVs) in domestic poultry have evolved in Korean poultry since 2007, genetic and serological comparisons were conducted of H9N2 isolates from poultry slaughterhouses from January 2008 to December 2009. The isolation rate was relatively low in 2008 but increased gradually from January 2009 onwards. Genetic and phylogenetic analyses revealed that reassortant viruses had emerged, generating at least five novel genotypes, mostly containing segments of a previously prevalent domestic H9N2 virus lineage (Ck/Korea/04116/04-like). It was noteworthy that the N2 genes of some H9N2 isolates (genotypes D, E and F) were derived from those of H3N2-like viruses commonly isolated among domestic ducks in live-poultry markets. Animal challenge studies demonstrated that the pathogenicity of Ck/Korea/SH0906/09 (genotype B) and Ck/Korea/SH0912/09 (genotype F) in domestic avian species was altered due to reassortment. Furthermore, serological analysis revealed that the isolates were antigenically distinct from previous Korean H9N2 viruses including Ck/Korea/01310/01. Such antigenic diversity was illustrated further in experiments using H9N2-immunized chickens, which could not inhibit the replication and transmission of challenge viruses from each genotype. These results suggest that H9N2 viruses from domestic poultry have undergone substantial evolution since 2007 by immune selection as a result of vaccinal and natural immunity, coupled with reassortment. Taken together, this study demonstrates that periodical updating of vaccine strains, based on continuous surveillance data, is an important issue in order to provide sufficient protectivity against AIV infections.

Isolation and characterization of cold-adapted strains producing beta-galactosidase.

beta-Galactosidase is extensively employed in the manufacture of dairy products, including lactose-reduced milk. Here, we have isolated two gram-negative and rod-shaped coldadapted bacteria, BS 1 and HS 39. These strains were able to break down lactose at low temperatures. Although two isolates were found to grow well at 10 degrees , the BS 1 strain was unable to grow at 37 degrees . Another strain, HS-39, evidenced retarded growth at 37 degrees . The biochemical characteristics and the results of 16S rDNA sequencing identified the BS 1 isolate as Rahnella aquatilis, and showed that the HS 39 strain belonged to genus Buttiauxella. Whereas the R. aquatilis BS 1 strain generated maximal quantities of beta-galactosidase when incubated for 60 h at 10 degrees , Buttiauxella sp. HS-39 generated beta-galactosidase earlier, and at slightly lower levels, than R. aquatilis BS 1. The optimum temperature for beta-galactosidase was 30 degrees for R. aquatilis BS-1, and was 45 degrees for Buttiauxella sp. HS-39, thereby indicating that R. aquatilis BS-1 was able to generate a cold-adaptive enzyme. These two cold-adapted strains, and most notably the beta-galactosidase from each isolate, might prove useful in some biotechnological applications.

Kinetic property and phylogenic relationship of 2-hydroxymuconic semialdehyde dehydrogenase encoded in tomC gene of Burkholderia cepacia G4.

2-Hydroxymuconic semialdehyde (2-HMS) dehydrogenase catalyzes the conversion of 2-HMS to 4-oxalocrotonate, which is a step in the meta cleavage pathway of aromatic hydrocarbons in bacteria. A tomC gene that encodes 2-HMS dehydrogenase of Burkholderia cepacia G4, a soil bacterium that can grow on toluene, cresol, phenol, or benzene, was overexpressed into E. coli HB101, and its gene product was characterized in this study. 2-HMS dehydrogenase from B. cepacia G4 has a high catalytic efficiency in terms of Vmax/Km towards 2-hydroxy-5-methylmuconic semialdehyde followed by 2-HMS but has a very low efficiency for 5-chloro-2-hydroxymuconic semialdehyde. However, the enzyme did not utilize 2-hydroxy-6-oxo-hepta-2,4-dienoic acid and 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid as substrates. The molecular weight of 2-HMS dehydrogenase from B. cepacia G4 was predicted to be 52 kDa containing 485 amino acid residues from the nucleotide sequence of the tomC gene, and it exhibited the highest identity of 78% with the amino acid sequence of 2-HMS dehydrogenase that is encoded in the aphC gene of Comamonas testosteroni TA441. 2-HMS dehydrogenase from B. cepacia G4 showed a significant phylogenetic relationship not only with other 2-HMS dehydrogenases, but also with different dehydrogenases from evolutionarily distant organisms.