Visible laser and UV-A radiation impact on a PNP degrading Moraxella strain and its rpoS mutant.

The role of stationary phase sigma factor gene (rpoS) in the stress response of Moraxella strain when exposed to radiation was determined by comparing the stress responses of the wild-type (WT) and its rpoS knockout (KO) mutant. The rpoS was turned on by starving the WT cultures for 24 h in minimal salt medium. Under non-starved condition, both WT and KO planktonic Moraxella cells showed an increase in mortality with the increase in duration of irradiation. In the planktonic non-starved Moraxella, for the power intensity tested, UV radiation caused a substantially higher mortality rate than did by the visible laser light (the mortality rate observed for 15-min laser radiation was 53.4 +/- 10.5 and 48.7 +/- 8.9 for WT and KO, respectively, and 97.6 +/- 0 and 98.5 +/- 0 for 25 s of UV irradiation in WT and KO, respectively). However, the mortality rate decreased significantly in the starved WT when exposed to these two radiations. In comparison, rpoS protected the WT against the visible laser light more effectively than it did for the UV radiation. The WT and KO strains of Moraxella formed distinctly different types of biofilms on stainless steel coupons. The KO strain formed a denser biofilm than did the WT. Visible laser light removed biofilms from the surfaces more effectively than did the UV. This was true when comparing the mortality of bacteria in the biofilms as well. The inability of UV radiation to penetrate biofilms due to greater rates of surface absorption is considered to be the major reason for the weaker removal of biofilms in comparison to that of the visible laser light. This result suggests that high power visible laser light might be an effective tool for the removal of biofilms.

Simultaneous determination of gene expression and bacterial identity in single cells in defined mixtures of pure cultures.

A protocol was developed to achieve the simultaneous determination of gene expression and bacterial identity at the level of single cells; a chromogenic beta-galactosidase activity assay was combined with in situ hybridization of fluorescently labelled oligonucleotide probes to rRNA. The method allows monitoring of gene expression and quantification of beta-galactosidase activity in single cells.

Some cultural characteristics of Branhamella ovis isolated from the conjunctival sac of sheep.

The colonial morphology and other cultural characteristics of Branhamella ovis were studied. The current investigation showed that colonies could be designated R (rough) and S (smooth) dependent on their appearance on agar. The colonial variants were apparently stable and each produced distinct types of pitting when grown on agar. A CAMP-like reaction was also shown to be a characteristic of B. ovis.

Density gradient centrifugation in urografin of Moraxella and Kingella cells and appendages.

Purification of fimbriae (pili) by density gradient banding in Urografin medium was attempted. Moraxella nonliquefaciens and Kingella kingae fimbriae were of higher density than their cells of origin, but fimbrial fractions obtained by homogenization and differential centrifugation still banded together with presumed outer membrane fragments and some whole cells in Urografin gradients. The cellular density of genetic variants with different fimbriation/competence levels was also studied. For one strain of M. nonliquefaciens and two strains of K. kingae, cells harvested from agar plates tended to show several bands on isopycnic density gradient centrifugation, with slightly higher general density of fimbriated variants than non-fimbriated. A single density band could be observed with cells from log phase broth cultures of selected strains which showed no distinct difference between fimbriation or competence variants of each strain. Cells of M. nonliquefaciens and M. bovis showed comparable buoyant densities, whereas those of K. kingae had a higher density.

Characterization and differentiation of 59 strains of Moraxella urethralis from clinical specimens.

The biochemical characteristics of 59 strains of Moraxella urethralis from clinical specimens, primarily from urine and the female genital tract, were studied. The characteristics included (i) the inability to acidify carbohydrate substrates, (ii) the ability to produce phenylalanine deaminase, (iii) the ability to reduce nitrite, (iv) the lack of urease activity, and (v) the ability of most strains to alkalinize citrate. A means of differentiating M. urethralis from Moraxella osloensis and Moraxella phenylpyruvica was determined.

Examination of two bacterial strains designated "Brucella suis biotype 5".

The morphological, cultural, biochemical, serological and pathogenic properties of two bacterial strains of the group designated ;Br. suis biotype 5' were examined. Both strains were found to be atypical of the genus Brucella in many of these characteristics. No serological relationship to known brucella strains could be detected. On the basis of the evidence obtained the two strains examined were classified as Moraxella duplex and the status of ;Br. suis biotype 5' questioned.

Ultrastructure of the cell wall and cytoplasmic membrane of gram-negative bacteria with different fixation techniques.

The ultrastructure of the cytoplasmic membrane and cell wall of two strains of Escherichia coli, Proteus morganii, P. vulgaris, Acinetobacter anitratum, Moraxella lacunata, Erwinia amylovora, Acinetobacter sp., and of a plant pathogen, unclassified gram-negative, fixed by the Ryter-Kellenberger procedure, was found to be significantly affected by the use or omission of the uranyl postfixation included in that procedure, and by the presence or absence of calcium in the OsO(4) fixative. The omission of the uranyl treatment results in a less clear profile of both the outer membrane of the cell wall and of the cytoplasmic membrane. The observation of these two membranes is further limited when both uranyl and calcium are omitted. The R-layer and the material covering the surface of the cell wall appear more distinct when the uranyl postfixation is not used. Evidence is given suggesting that the influence of uranyl and calcium ions on the appearance of the outer and cytoplasmic membranes would be primarily due to their action as fixatives, whereas the influence of uranyl on the appearance of the R-layer would be due to a direct action on the peptidoglycan component of this layer. When uranyl acetate is used as a section stain after the embedding in plastic, it improves the observation of the R-layer. In this case, a well contrasted R-layer is consistently observed in all strains studied, provided that the postfixation has been omitted. The frequent difficulty in clearly observing the R-layer in many published micrographs probably results from the common use of uranyl postfixation.