Geology topics
J.A. Bader
Publications and source records attributed to J.A. Bader.
Identification of Flavobacterinium and Flexibacterin species by species-specific polymerase chain reaction primers to the 16S ribosomal RNA gene
Species-specific polymerase chain reaction (PCR) primers have been developed for the identification of the causative agents of warmwater and marine finrot in fish: Flavobacterium columnare ( Flexibacter columnaris ) and Flexibacter maritimus. Differences in gene sequence in the bacterial small-subunit (16S) ribosomal RNA (rRNA) were used to design the species-specific PCR primers. The previously reported species-specific PCR primers Psy1 and Psy2 for the identification of Flavobacterium psychrophilum ( Flexibacter psychrophila ), the causative agent of coldwater finrot, were also used to develop a speciation scheme for all three bacterial finrots. These three primer sets were successful in discriminating among yellow-pigmented bacteria as well as in speciating the three major pathogenic flexibacteria to fish. The primer sets were designed to produce uniquely sized subproducts of 16S rRNA for each species: Flavobacterium psychrophilum (1,100 base pairs, bp), F. columnare (800 bp), and Flexibacter maritimus (400 bp). These primers were shown to correctly speciate field isolates in double-blind experiments ( P = 0.01).
Determination of phylogenetic relationships of Flavobacterinium psychrophilum (Flexibacterin psychrophilus), Flavobacterinium columnare (Flexibacterin columnaris), and Flexibacterin maritimus by sequence analysis of 16S ribosomal RNA genes amplified by polymerase chain reaction
The nearly complete small subunit 16S ribosomal RNA (rRNA) gene sequence amplified by polymerase chain reaction was determined for Flavobacterium psychrophilum (formerly Flexibacter psychrophilus ) by using automated nucleotide sequencing. The sequence was found to be 1,465 base pairs (bp) in length, a size consistent with previously determined sequences for 14 other bacterial species from various taxa, including the yellow-pigmented bacteria. Sequence signatures confirmed that this organism was a member of the bacterial division Bacteroides–Flavobacterium. Parsimonious and additive phylogenetic trees were constructed with homology, and pairwise evolutionary distances were used to estimate phylogenetic relationships. Data show that F. psychrophilum, F. columnare , and Flexibacter maritimus are closely related, have a common descent, and represent a distinct group within the division Bacteroides–Flavobacterium. This group also included other organisms from the genera Flavobacterium and Cytophaga. Further, Flavobacterium aquatile , the type species for the genus Flavobacterium , was also determined to be a member of this “ Flavobacterium–Cytophaga–Flexibacter subcomplex.” This supports previous assertions that the type strain of Flavobacterium should be changed to a more representative species such as Flavobacterium breve .
Occurrence of Loma cf salmonae brook, brown and rainbow trout from Buford Trout Hatchery, Georgia, USA
During a 6 mo study of moribund trout from Buford hatchery, Buford, Georgia, USA, a Loma cf. salmonae microsporidian parasite was studied in the gills of brook trout Salvelinus fontinalis , brown trout Salmo trutta , and rainbow trout Oncorhynchus mykiss . This parasite was morphologically similar to L. salmonae and L. fontinalis but differed in spore size. Scanning and transmission electron microscopy demonstrated that xenomas were embedded in gill filaments. Transmission electron micrographs prepared from fresh tissue showed mature spores with 12 to 15 turns of their polar tube. Spore diameters for the Georgia strain from formalin-fixed gill tissues measured 3.5 (SD ±0.1) by 1.8 (SD ±0.1) µm. Electron micrographs of formalin-fixed, deparaffinized tissues of rainbow trout from Pennsylvania and West Virginia show spores with a diameter of 3.5 (±0.2) by 1.7 (±0.1) µm and 3.4 (±0.2) by 1.8 (±0.1) µm, respectively. Transmission electron micrographs of spores from Pennsylvania and West Virginia show that mature spores from both states had 13 to 15 turns of their polar tubes. Measurements from transmission electron micrographs prepared from alcohol-fixed tissues from Virginia fish contained spores with a diameter of 3.0 (±0.3) by 1.1 (±0.3) µm and 12 to 15 turns of their polar tubes. These measurements are consistent with L. salmonae and therefore suggest that the parasite is present on the east coast of the United States. During the height of the Georgia epizootic, the percentage of fish with observed xenomas reached 62.2% (N = 87), and the highest number of xenomas counted per 10 gill filaments was 133 (N = 87). The microsporidian epizootic occurred either during the autumn months or when intake river water quality reached combined iron-manganese concentrations as high as 1.01 (mean 0.44, SD ±0.42) mg -1 .