Macrophyte species composition,distribution and diversity in relation to some physicochemical factors in the littoral zone of Lake Ziway,Ethiopia

The species composition, distribution and diversity of macrophytes in Lake Ziway were determined at the end of dry and wet seasons along nine littoral sites during 2010 using a belt transect method. Some physicochemical parameters were also measured. Fourteen macrophyte species were identified with low species diversity for the lake (H' value of 1.805). The macrophyte species composition of the lake has undergone many changes during the last few decades. Arundo donax, which was never reported earlier, attained the highest relative density (30.7%) and frequency (30.5%) in this study, followed by Echinochloa colona, Potamogeton schweinfurthii, Cyperus articulatus, Typha latifolia and Cyperus papyrus. The average densities of A. donax, C. articulatus, E. colona and Pistia stratiotes were positively correlated with nutrients, whereas the density of the other species had negative correlation with physicochemical variables (CCA). Generally, the present macrophyte composition and abundance indicates healthy ecological condition of the lake. But if nutrient levels continue to increase and water levels continue to decline, we expect further changes in macrophyte composition and especially a shift towards invasive floating species.     

Bacteriocin Production, Antibiotic Susceptibility and Prevalence of Haemolytic and Gelatinase Activity in Faecal Lactic Acid Bacteria Isolated from Healthy Ethiopian Infants

The objective of this study was to characterise lactic acid bacteria (LAB) isolated from faecal samples of healthy Ethiopian infants, with emphasis on bacteriocin production and antibiotic susceptibility. One hundred fifty LAB were obtained from 28 healthy Ethiopian infants. The isolates belonged to Lactobacillus (81/150), Enterococcus (54/150) and Streptococcus (15/150) genera. Lactobacillus species were more abundant in the breast-fed infants while Enterococcus dominated the mixed-fed population. Bacteriocin-producing LAB species were isolated from eight of the infants. Many different bacteriocins were identified, including one new bacteriocin from Streptococcus salivarius, avicin A (class IIa) from Enterococcus avium, one class IIa bacteriocin from Enterococcus faecalis strains, one unknown bacteriocin from E. faecalis and two unknown bacteriocins from Lactobacillus fermentum strains and the two-peptide gassericin T from Lactobacillus gasseri isolate. Susceptibility tests performed for nine antibiotics suggest that some lactobacilli might have acquired resistance to erythromycin (3 %) and tetracycline (4 %) only. The streptococci were generally antibiotic sensitive except for penicillin, to which they showed intermediate resistance. All enterococci were susceptible to ampicillin while 13 % showed penicillin resistance. Only one E. faecalis isolate was vancomycin-resistant. Tetracycline (51 %) and erythromycin (26 %) resistance was prevalent among the enterococci, but multidrug resistance was confined to E. faecalis (47 %) and Enterococcus faecium (33 %). Screening of enterococcal virulence traits revealed that 2 % were β-haemolytic. The structural genes of cytolysin were detected in 28 % of the isolates in five enterococcal species, the majority being E. faecalis and Enterococcus raffinosus. This study shows that bacteriocin production and antibiotic resistance is a common trait of faecal LAB of Ethiopian infants while virulence factors occur at low levels.     

Prospecting Environmental Mycobacteria: Combined Molecular Approaches Reveal Unprecedented Diversity

Background

Environmental mycobacteria (EM) include species commonly found in various terrestrial and aquatic environments, encompassing animal and human pathogens in addition to saprophytes. Approximately 150 EM species can be separated into fast and slow growers based on sequence and copy number differences of their 16S rRNA genes. Cultivation methods are not appropriate for diversity studies; few studies have investigated EM diversity in soil despite their importance as potential reservoirs of pathogens and their hypothesized role in masking or blocking M. bovis BCG vaccine.

Methods

We report here the development, optimization and validation of molecular assays targeting the 16S rRNA gene to assess diversity and prevalence of fast and slow growing EM in representative soils from semi tropical and temperate areas. New primer sets were designed also to target uniquely slow growing mycobacteria and used with PCR-DGGE, tag-encoded Titanium amplicon pyrosequencing and quantitative PCR.

Results

PCR-DGGE and pyrosequencing provided a consensus of EM diversity; for example, a high abundance of pyrosequencing reads and DGGE bands corresponded to M. moriokaense, M. colombiense and M. riyadhense. As expected pyrosequencing provided more comprehensive information; additional prevalent species included M. chlorophenolicum, M. neglectum, M. gordonae, M. aemonae. Prevalence of the total Mycobacterium genus in the soil samples ranged from 2.3×10⁷ to 2.7×10⁸ gene targets g⁻¹; slow growers prevalence from 2.9×10⁵ to 1.2×10⁷ cells g⁻¹.

Conclusions

This combined molecular approach enabled an unprecedented qualitative and quantitative assessment of EM across soil samples. Good concordance was found between methods and the bioinformatics analysis was validated by random resampling. Sequences from most pathogenic groups associated with slow growth were identified in extenso in all soils tested with a specific assay, allowing to unmask them from the Mycobacterium whole genus, in which, as minority members, they would have remained undetected.     

Subcellular distribution of ZP1, ZP2, and ZP3 glycoproteins during folliculogenesis and demonstration of their topographical disposition within the zona matrix of mouse ovarian oocytes

The zona pellucida (ZP) is an extracellular coat synthesized and secreted by the oocyte during follicular development and surrounding the plasma membrane of mammalian eggs. To date, the mechanism of synthesis and secretion, mode of assembly, and intracellular trafficking of the ZP glycoproteins have not been fully elucidated. Using antibodies against mouse ZP1, ZP2, and ZP3 in conjunction with the protein A-gold technique, we have shown an association of immunolabeling with the Golgi apparatus, secretory granules, and a complex structure called vesicular aggregate, respectively, in mouse ovarian follicles. In contrast, the neighboring granulosa cells were not reactive to any of the three antibodies used. Immunolabeling of ZP1, ZP2, and ZP3 was detected throughout the entire thickness of the ZP, irrespective of the developmental stage of ovarian follicles. Double and triple immunolocalization studies, using antibodies tagged directly to different sizes of gold particles, revealed an asymmetric spatial distribution of the three ZP glycoproteins in the zona matrix at various stages of follicular development. All three glycoproteins were specifically localized over small patches of darkly stained flocculent substance dispersed throughout the zona matrix. Very often, ZP1, ZP2, and ZP3 were found in close association. These results confirm findings from previous studies demonstrating that ovarian oocytes and not granulosa cells are the only source for mouse ZP glycoproteins. In addition, results from our morphological and immunocytochemical experiments suggest that the vesicular aggregates in the ooplasm are likely to serve as an intermediary in the synthesis and secretion of ZP glycoproteins. The stoichiometric disposition of ZP1, ZP2, and ZP3 in the zona matrix as revealed by double and triple immunolocalization studies provide further insight into some of the unanswered questions pertinent to the current model of mouse ZP structure proposed by the Wassarman group.