Phylogeny of the hard ticks (Ixodidae) inferred from 18S rRNA indicates that the genus Aponomma is paraphyletic.

We examined the phylogeny of ticks (Acari:Parasitiformes:Ixodida) and their closest known mite relatives (Acari:Parasitiformes:Mesostigmata and Holothyrida) using 18S rRNA sequences. In our analyses, we included sequences from 36 taxa. Sequences for 13 hard ticks (Family Ixodidae), 5 soft ticks (Family Argasidae), and 2 mesostigmatid mites were obtained from the GenBank database and we generated sequences for 15 hard ticks and 1 holothyrid mite. Ten of these tick species were endemic to Australia. Our analyses indicated that the suborder Holothyrida is more closely related to Ixodida than to Mesostigmata, the group used as outgroup in earlier molecular studies. This finding is consistent with Lehtinen's (1991) hypothesis that the Holothyrida rather than the Mesostigmata is the sister-group to the Ixodida. Within the hard ticks the genus Aponomma and thus the family Amblyomminae were paraphyletic. Taxonomic revision of these taxa is needed. The genus Amblyomma was paraphyletic without the inclusion of "typical" Aponomma species (Ap. latum and Ap. fimbriatum). There was a basal divergence between endemic Australian and other species in both the Metastriata and the Prostriata divisions of the hard ticks.

Flavobacterium hibernum sp. nov., a lactose-utilizing bacterium from a freshwater Antarctic lake.

Four freshwater Antarctic lakes were examined for the presence of beta-galactosidase-producing bacteria using mineral medium enrichments and lactose. Enrichments from only one of the lakes produced growth and two strains were isolated that were very similar in phenotype and fatty acid profile, and shared considerable homology in their DNA (DNA-DNA hybridization = 93 +/- 7%). The strains were psychrotrophic with theoretical Tmax, Tmin and Topt of 30-31, -7 degrees and 26 degrees C, respectively. The beta-galactosidase in cell extracts had an optimal activity at 39 degrees C. The strains were Gram-negative rods, showed gliding motility, contained branched and hydroxy fatty acids, and menaquinone 6 as the major respiratory quinone. The strains did not form microcysts and utilized lactose while using ammonium ions as a source of nitrogen, and a range of other sugars. The G + C content of the DNA was 34 mol%. Phylogenetic analysis of one of the strains, by comparison of 16S rDNA sequences, showed that it was most similar, but not identical to, Flavobacterium columnare and '[Sporocytophaga] cauliformis'. Both species could be differentiated phenotypically from the Antarctic isolates. DNA-DNA hybridization of the Antarctic isolate with six different members of the Flavobacterium 16S rDNA cluster showed no strain with greater than 18% relatedness. The nearest type species to the Antarctic isolate in the phylogenetic analysis was Flavobacterium aquatile. The name Flavobacterium hibernum is proposed for the Antarctic strains, and the type strain is ATCC 51468T (= ACAM 376T).

Fast image-quality-based optimization of optical systems.

The performance is reported of new optimization software that maximizes the relative modulation transfer function (MTF) by minimizing the merit function (1 minus the approximate relative MTF). Contrary to the predictions of earlier studies, this merit function, whose only variable part is the variance of the wave aberration difference function, is shown to be effective for both poorly and well-corrected systems. In addition, the new software is significantly faster than our in-house software for the direct optimization of the actual MTF.

Accurate calculation of Narcissus signatures by using finite ray tracing.

In scanning IR systems with cooled quantum detectors, the Narcissus signature usually has a limiting effect on the perceived image quality, and so it is important that it be assessed accurately before manufacture. We describe a new finite ray-tracing method in which each ray represents an equal amount of flux falling on the detector. Such methods require many rays; therefore a full error treatment is given that allows designers to estimate the necessary number of rays to obtain the required accuracy and also to calculate the standard deviation of the error in the final computed result.

Calculation and optimization of Narcissus using paraxial ray tracing.

The Narcissus effect occurs in IR optical systems that employ a cooled quantum detector and can degrade the image quality very severely. Therefore, it is essential that it is controlled in the design stage. A detailed description is given of how Narcissus can be calculated, by the use of a routine based on paraxial ray tracing, and reduced automatically and simultaneously with the system aberrations, by inclusion of its results in the merit function of a damped least-squares optimization program.

Reevaluating the classification of Paracoccus halodenitrificans with sequence comparisons of 16S ribosomal DNA.

The results of phylogenetic analysis in which 16S ribosomal DNA sequences were compared confirmed previous chemotaxonomic data which suggested that Paracoccus halodenitrificans is inappropriately placed in the genus Paracoccus, which belongs in the alpha subclass of the Proteobacteria. P. halodenitrificans should be placed in the family Halomonadaceae, which belongs in the gamma subclass of the Proteobacteria.

Phylogenetic relationships between some members of the genera Deleya, Halomonas, and Halovibrio.

The genera Halomonas and Deleya, which constitute the family Halomonadaceae, are difficult to differentiate on the basis of phenotypic and chemotaxonomic attributes. DNA-rRNA hybridization studies have indicated that some Halomonas spp. have the same level of relationship to the type species of the genus Deleya as some Deleya spp. A phylogenetic analysis of the 16S rRNA sequences of seven members of the Halomonadaceae indicated that the members of the genera Halomonas and Deleya do not form separate monophyletic subgroups, confirming the lack of any phylogenetic support for retention of these taxa as separate genera. A phylogenetic analysis of the 16S rRNA sequence of Halovibrio variabilis confirmed that this species belongs in the Halomonadaceae. All of the members of the Halomonadaceae examined and Halovibrio variabilis possess a cytosine residue at position 486 (Escherichia coli numbering), which is an extremely rare attribute among the prokaryotes and has been reported in only one other species, Listonella anguillarum. Several other signature characteristics which define this group in the gamma subclass of the Proteobacteria are identified. The Jukes-Cantor distances between members of the family Halomonadaceae, including Halovibrio variabilis, range from 0.086 to 0.000 (the levels of similarity between the 16S rRNA sequences range from 92.6 to 100%). The members of the genera Halomonas, Deleya, and Halovibrio form a monophyletic group and share common chemotaxonomic and phenotypic characteristics. Subgroups containing members of the genera Halomonas, Deleya, and Halovibrio cannot be resolved on the basis of phylogenetic, chemotaxonomic, or phenotypic data. Our data indicate that the members of the genera Halomonas, Deleya, and Halovibrio should be united in a single genus.

Direct sequencing of the polymerase chain reaction-amplified 16S rRNA gene of Flavobacterium gondwanense sp. nov. and Flavobacterium salegens sp. nov., two new species from a hypersaline Antarctic lake.

Phenotypic data and phospholipid ester-linked fatty acid profiles indicate that pigmented bacterial strains isolated from a hypersaline Antarctic lake are members of the "flavobacterium-bacteroides" phylum and may represent new taxa. Nearly complete 16S rRNA sequences were obtained for representative strains by directly sequencing the polymerase chain reaction-amplified 16S rRNA gene. Sequence signatures confirmed that these organisms were members of the flavobacterium-bacteroides phylum. A phylogenetic analysis, in which the sequences of the Antarctic strains were compared with a large number of sequences available for members of the flavobacterium-bacteroides phylum, showed that the Antarctic strains were phylogenetically distinct. The new species cluster with a group of organisms that contains the type species of the genus Flavobacterium, Flavobacterium aquatile. Two new species are described, for which the names Flavobacterium gondwanense and Flavobacterium salegens are proposed; strains ACAM 44 (= DSM 5423) and ACAM 48 (= DSM 5424) are the type strains of F. gondwanense and F. salegens, respectively.

Cell wall-less, free-living spirochetes in Antarctica.

The phylogeny of an Antarctic, cell wall-less, bacterial strain was determined by sequencing PCR amplified 16S rDNA, and comparison of the sequence with other bacterial 16S rRNA sequences available in databanks. Although the strain was phenotypically very similar to members of the genus Anaeroplasma, phylogenetic analyses showed it was a member of the order Spirochaetales. Until now, the order was one of the few bacterial orders in which phylogeny was reflected in a uniform morphology of its members. The viability of wall-less cells in cultures of spirochetes and spirochetal infective material warrants reinvestigation.

A dual viewing attachment with the hand-held ophthalmoscope.

A flexible dual viewing attachment for a hand-held ophthalmoscope permits rapid and effective instruction of undergraduate medical students in the ophthalmoscopic technique.