Virulence variations between clonal complexes of Melisococcus plutonius and the possible causes.

Melissococcus plutonius is a pathogenic bacterium that affects honeybee brood triggering colony collapse in severe cases. The bacterium causes a European foulbrood (EFB) disease in the honeybee populations, impacting beekeeping and agricultural industries. The pathogenesis, epidemiology, and variants of M. plutonius have been studied, but the virulence factors involved in larval infection are still unknown. Recently, an in-silico study suggested putative genes that might play a role in the pathogenesis of EFB. However, studies are required to determine their function as virulence factors. In addition, the few studies of clonal complexes (CCs), virulence factors, and variation in the honeybee larvae mortality have interfered with the development of more efficient control methods. The research, development, and differences in virulence between genetic variants (CCs) of M. plutonius and potential virulence factors implicated in honeybee larval mortality are discussed in this review.

Method-induced variation in the bacterial cell surface hydrophobicity MATH test.

Bacterial cell surface hydrophobicity is a relevant property in determining the ability of bacteria to adhere to inert surfaces. This property has been measured using the microbial adhesion to hydrocarbon (MATH) test. Several reports in the literature establish the percentage of adhesion to hydrocarbons (PoAtH) value produced by the MATH test for a broad variety of bacteria. Discrepancies in PoAtH values reported for the same strain of a specific microorganism suggest that some method-induced variation may exist, as different research teams employ different versions of the assay. The objective of the present study was to compare the performance of different versions of the MATH test as reported in the literature, to quantify the magnitude of the method-induced variation on PoAtH values. The study demonstrated that PoAtH values are influenced twice as much by variations in the employed assay than by actual differences in cell surface composition or architecture. The two L. reuteri strains studied responded differently to changes in assay conditions showing 40 and 70% method-dependent variation for strain ATCC 53609 and 55730, respectively. These results highlight the need to properly standardize the MATH test to enable comparison of PoAtH values produced by independent research teams.

Prevalence, typing and phylogenetic analysis of Melissococcus plutonius strains from bee colonies of the State of Chihuahua, Mexico.

European foulbrood (EFB) caused by Melissococcus plutonius is an important bee brood disease but, in Mexico, information about this bacterium is limited. We evaluated the prevalence of typical and atypical strains in beehives of seven apicultural regions of the state of Chihuahua, Mexico. We performed MLST and phylogenetic analysis to characterize the isolates. Prevalence was highest 59%, in the region of Chihuahua, and lowest, 14%, in the regions of Cuauhtémoc and Nuevo Casas Grandes. Typical and atypical strains were identified in hives from all regions; however, in the regions of Parral, Cuauhtémoc and Aldama, the atypical strains were only detected in combination with typical strains. We obtained 81 isolates of M. plutonius and identified seven sequence types, of which three were new types. Additionally, we observed a relation between sequence type and the region where the strain was isolated. Phylogenetic analysis and multilocus sequence typing using goeBURST analysis showed that 97.5% of the isolates correspond to the Clonal Complex (CC) 12 and 2.5% to the CC3. Our work is the first molecular characterization of M. plutonius in Mexico and contributes to global information about the epidemiology of this pathogen.

Identification of avocado (Persea americana) root proteins induced by infection with the oomycete Phytophthora cinnamomi using a proteomic approach.

Avocado root rot, caused by Phytophthora cinnamomi, is the most important disease that limits avocado production. A proteomic approach was employed to identify proteins that are upregulated by infection with P. cinnamomi. Different proteins were shown to be differentially expressed after challenge with the pathogen by two-dimensional (2-D) gel electrophoresis. A densitometric evaluation of protein expression indicated differential regulation during the time-course analyzed. Some proteins induced in response to the infection were identified by standard peptide mass fingerprinting using matrix-assisted laser desorption/ionization-time of flight-mass spectrometry and sequencing by MALDI LIFT-TOF/TOF tandem mass spectrometry. Of the 400 protein spots detected on 2-D gels, 21 seemed to change in abundance by 3 hours after infection. Sixteen proteins were upregulated, 5 of these were only detected in infected roots and 11 showed an increased abundance. Among the differentially expressed proteins identified are homologs to isoflavone reductase, glutathione S-transferase, several abscisic acid stress-ripening proteins, cinnamyl alcohol dehydrogenase, cinnamoyl-CoA reductase, cysteine synthase and quinone reductase. A 17.3-kDa small heat-shock protein and a glycine-rich RNA-binding protein were identified as downregulated. Our group is the first to report on gene induction in response to oomycete infection in roots from avocado, using proteomic techniques.