Structure of the peptidoglycans of Moraxella glucidolytica and Moraxella lwoffi grown on hydrocarbons

The peptidoglycans of Moraxella glucidolytica and Moraxella lwoffi grown on aliphatic hydrocarbons were isolated. They contained muramic acid. glucosamine, alanine, d-glutamic acid and meso-diaminopimelic acid in a molar ratio of about 0.5:0.5:1.6:1.0:1.0 (M. glucidolytica) and 0.8:0.7:1.3:1.0:1.0 (M. lwoffi).The peptidoglycans were lysozyme-resistant. However, when treated with formamide, they could be partially degraded by lysozyme. The fragments were purified and their structure determined. In both strains, the peptide subunits consisted mainly of tripeptides (l-Ala-d-Glu-meso-DAP) and tetrapeptides (l-Ala-d-Glu-meso-DAP-d-Ala), most of them being directly cross-linked. It is concluded that in both strains the primary structures of the peptidoglycans are closely related.     

A Novel Group of Moraxella catarrhalis UspA Proteins Mediates Cellular Adhesion via CEACAMs and Vitronectin

Moraxella catarrhalis (Mx) is a common cause of otitis media and exacerbation of chronic obstructive pulmonary disease, an increasing worldwide problem. Surface proteins UspA1 and UspA2 of Mx bind to a number of human receptors and may function in pathogenesis. Genetic recombination events in the pathogen can generate hybrid proteins termed UspA2H. However, whether certain key functions (e.g. UspA1-specific CEACAM binding) can be exchanged between these adhesin families remains unknown. In this study, we have shown that Mx can incorporate the UspA1 CEACAM1-binding region not only into rare UspA1 proteins devoid of CEACAM-binding ability, but also into UspA2 which normally lack this capacity. Further, a screen of Mx isolates revealed the presence of novel UspA2 Variant proteins (UspA2V) in ∼14% of the CEACAM-binding population. We demonstrate that the expression of UspA2/2V with the CEACAM-binding domain enable Mx to bind both to cell surface CEACAMs and to integrins, the latter via vitronectin. Such properties of UspA2/2V have not been reported to date. The studies demonstrate that the UspA family is much more heterogeneous than previously believed and illustrate the in vivo potential for exchange of functional regions between UspA proteins which could convey novel adhesive functions whilst enhancing immune evasion.     

Defined medium for Moraxella bovis

A defined medium (medium MB) for Moraxella bovis was formulated. Nineteen strains grew well on medium MB. One strain was auxotrophic for asparagine, and another was auxotrophic for methionine. Strains of M. equi and M. lacunata also grew on medium MB. All strains had an absolute requirement for thiamine and were stimulated by or actually required the other growth factors in the medium.     

Selective Medium for Moraxella nonliquefaciens

A medium is described which selectively inhibits most bacteria from the normal flora of the conjunctiva, the lid-margin, and the upper respiratory tract but permits growth of Moraxella nonliquefaciens, M. liquefaciens, and the less fastidious strains of M. lacunata. The selective conditions are obtained with thiostrepton, tyrothricin, and sodium nalidixinate as inhibitors. Incubation under increased CO(2) pressure increased the number of primary isolations. M. nonliquefaciens was isolated on the selective medium twice as many times as on other media.     

Interesting sequence differences between the pilin gene inversion regions of Moraxella lacunata ATCC 17956 and Moraxella bovis Epp63.

The bacterium Moraxella lacunata is a causative agent of human conjunctivitis and keratitis. We have previously reported construction of plasmid pMxL1, which includes a 5.9-kb fragment on which the pilin gene inversion region of M. lacunata resides. The inversion region of pMxL1 was shown to invert when pMxL1 was in an Escherichia coli host cell. In this report, we present Western immunoblot analysis using Moraxella bovis Epp63 anti-I and anti-Q pilin sera which demonstrate that pMxL1 makes pilin only when in orientation 1. The sequence of the pMxL1 plasmid containing the invertible region contains a perfect tandem repeat of 19 bp in the orientation 1 nonexpressed pilin gene at the middle of the recombination junction site. This 19-bp insert causes a frameshift and disrupts the pilin gene. The predicted amino acid sequence of this nonfunctional pilin gene (with the 19-bp repeat subtracted) bears closest resemblance to M. bovis Epp63 Q pilin sequence, although the other (functional) M. lacunata pilin encoded by pMxL1 shows slightly higher homology to Q pilin. Comparison of the pMxL1 sequence with that of the M. bovis Epp63 sequence shows two other particularly interesting differences. One is a 15-bp sequence addition found in pMxL1 at the 60-bp region previously reported as a possible M. bovis recombinational enhancer. The second is an AT deletion in pMxL1 compared with Epp63 within an open reading frame (tfpB) which results in the pMxL1 tfpB open reading frame being one-third shorter than in Epp63. The DNA sequences in these three altered regions from the M. lacunata strain from which pMxL1 was derived were amplified by polymerase chain reaction and sequenced. The parent strain was found to contain the differences seen in pMxL1. Comparison of the M.bovis and M. lacunata pilin gene amino acid sequences is also presented.     

Two sequence-specific endonucleases from Moraxella bovis

Two new sequence-specific endodeoxyribonucleases have been partially purified from Moraxella bovis. These restriction-like enzymes, MboI and MboII, each cleave bacteriophage lambda DNA and adenovirus-2 DNA at more than 50 sites. MboI recognizes the sequence 5′ ↓ G-A-T-C 3′ 3′ C-T-A-G ↑ 5′ and cleaves at the sites indicated by the arrows. A specific endonuclease, MosI, has also been purified from Moraxella osloenis and recognizes the same sequence as MboI.     

Molecular Aspects of Moraxella catarrhalis Pathogenesis

Summary: In recent years, Moraxella catarrhalis has established its position as an important human mucosal pathogen, no longer being regarded as just a commensal bacterium. Further, current research in the field has led to a better understanding of the molecular mechanisms involved in M. catarrhalis pathogenesis, including mechanisms associated with cellular adherence, target cell invasion, modulation of the host''s immune response, and metabolism. Additionally, in order to be successful in the host, M. catarrhalis has to be able to interact and compete with the commensal flora and overcome stressful environmental conditions, such as nutrient limitation. In this review, we provide a timely overview of the current understanding of the molecular mechanisms associated with M. catarrhalis virulence and pathogenesis.     

Characterization of the first molluscicidal lipopolysaccharide from Moraxella osloensis

Moraxella osloensis is a bacterium that is mutualistically associated with Phasmarhabditis hermaphrodita, a nematode that has potential for the biocontrol of mollusk pests, especially the slug Deroceras reticulatum. We discovered that purified M. osloensis lipopolysaccharide (LPS) possesses a lethal toxicity to D. reticulatum when administered by injection but no contact or oral toxicity to this slug. The toxicity of the LPS resides in the lipid A moiety. M. osloensis LPS was semiquantitated at 6 x 10(7) endotoxin units per mg. The LPS is a rough-type LPS with an estimated molecular weight of 5,300. Coinjection of galactosamine with the LPS increased the LPS's toxicity to the slug two- to four-fold. The galactosamine-induced sensitization of the slug to the LPS was reversed completely by uridine.