Effect of Dietary Chestnut or Quebracho Tannin Supplementation on Microbial Community and Fatty Acid Profile in the Rumen of Dairy Ewes

Ruminants derived products have a prominent role in diets and economy worldwide; therefore, the capability to control the rumen microbial ecosystem, for ameliorating their quality, is of fundamental importance in the livestock sector. The aim of this study was to evaluate the effect of dietary supplementation with chestnut and quebracho tannins on microbial community and fatty acid profile, in the rumen fluid of dairy ewes. Multivariate analysis of PCR-DGGE profiles of rumen microbial communities showed a correlation among the presence of chestnut or quebracho in the diet, the specificButyrivibriogroup DGGE profiles, the increase in 18:3cis9,cis12, andcis15; 18:2cis9 andcis12; 18:2cis9 andtrans11; 18:2trans11 andcis15; and 18:1trans11 content, and the decrease in 18:0 concentration. Phylogenetic analysis of DGGE band sequences revealed the presence of bacteria representatives related to the generaHungatella,Ruminococcus, andEubacteriumand unclassified Lachnospiraceae family members, suggesting that these taxa could be affected by tannins presence in the diets. The results of this study showed that tannins from chestnut and quebracho can reduce the biohydrogenation of unsaturated fatty acids through changes in rumen microbial communities.

Vertical Transmission of a Phylogenetically Complex Microbial Consortium in the Viviparous Sponge Ircinia felix

ABSTRACT Many marine demosponges contain large amounts of phylogenetically complex yet highly sponge-specific microbial consortia within the mesohyl matrix, but little is known about how these microorganisms are acquired by their hosts. Settlement experiments were performed with the viviparous Caribbean demosponge Ircinia felix to investigate the role of larvae in the vertical transmission of the sponge-associated microbial community. Inspections by electron microscopy revealed large amounts of morphologically diverse microorganisms in the center of I. felix larvae, while the outer rim appeared to be devoid of microorganisms. In juveniles, microorganisms were found between densely packed sponge cells. Denaturing gradient gel electrophoresis (DGGE) was performed to compare the bacterial community profiles of adults, larvae, and juvenile sponges. Adults and larvae were highly similar in DGGE band numbers and banding patterns. Larvae released by the same adult individual contained highly similar DGGE banding patterns, whereas larvae released by different adult individuals showed slightly different DGGE banding patterns. Over 200 bands were excised, sequenced, and phylogenetically analyzed. The bacterial diversity of adult I. felix and its larvae was comparably high, while juveniles showed reduced diversity. In total, 13 vertically transmitted sequence clusters, hereafter termed “IF clusters,” that contained sequences from both the adult sponge and offspring (larvae and/or juveniles) were found. The IF clusters belonged to at least four different eubacterial phyla and one possibly novel eubacterial lineage. In summary, it could be shown that in I. felix, vertical transmission of microorganisms through the larvae is an important mechanism for the establishment of the sponge-microbe association.

Fluorophore-Labeled Primers Improve the Sensitivity, Versatility, and Normalization of Denaturing Gradient Gel Electrophoresis

ABSTRACT Denaturing gradient gel electrophoresis (DGGE) is widely used in microbial ecology. We tested the effect of fluorophore-labeled primers on DGGE band migration, sensitivity, and normalization. The fluorophores Cy5 and Cy3 did not visibly alter DGGE fingerprints; however, 6-carboxyfluorescein retarded band migration. Fluorophore modification improved the sensitivity of DGGE fingerprint detection and facilitated normalization of samples from multiple gels by the application of intralane standards.

Molecular Analysis of Diazotroph Diversity in the Rhizosphere of the Smooth Cordgrass, Spartina alterniflora

ABSTRACT N2 fixation by diazotrophic bacteria associated with the roots of the smooth cordgrass, Spartina alterniflora, is an important source of new nitrogen in many salt marsh ecosystems. However, the diversity and phylogenetic affiliations of these rhizosphere diazotrophs are unknown. Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified nifH sequence segments was used in previous studies to examine the stability and dynamics of the Spartina rhizosphere diazotroph assemblages in the North Inlet salt marsh, near Georgetown, S.C. In this study, plugs were taken from gel bands from representative DGGE gels, thenifH amplimers were recovered and cloned, and their sequences were determined. A total of 59 sequences were recovered, and the amino acid sequences predicted from them were aligned with sequences from known and unknown diazotrophs in order to determine the types of organisms present in the Spartina rhizosphere. We recovered numerous sequences from diazotrophs in the γ subdivision of the division Proteobacteria(γ-Proteobacteria) and from various anaerobic diazotrophs. Diazotrophs in the α-Proteobacteria were poorly represented. None of the Spartina rhizosphere DGGE band sequences were identical to any known or previously recovered environmental nifH sequences. TheSpartina rhizosphere diazotroph assemblage is very diverse and apparently consists mainly of unknown organisms.