Elimination Of Protozoa Research Articles

Dynamics of methanogenesis, ruminal fermentation and fiber digestibility in ruminants following elimination of protozoa: a meta-analysis

BackgroundRuminal microbes are vital to the conversion of lignocellulose-rich plant materials into nutrients for ruminants. Although protozoa play a key role in linking ruminal microbial networks, the contribution of protozoa to rumen fermentation remains controversial; therefore, this meta-analysis was conducted to quantitatively summarize the temporal dynamics of methanogenesis, ruminal volatile fatty acid (VFA) profiles and dietary fiber digestibility in ruminants following the elimination of protozoa (also termed defaunation). A total of 49 studies from 22 publications were evaluated.ResultsThe results revealed that defaunation reduced methane production and shifted ruminal VFA profiles to consist of more propionate and less acetate and butyrate, but with a reduced total VFA concentration and decreased dietary fiber digestibility. However, these effects were diminished linearly, at different rates, with time during the first few weeks after defaunation, and eventually reached relative stability. The acetate to propionate ratio and methane production were increased at 7 and 11 wk after defaunation, respectively.ConclusionsElimination of protozoa initially shifted the rumen fermentation toward the production of more propionate and less methane, but eventually toward the production of less propionate and more methane over time.

The gamut of host immune responses and immunopathology in parasitic diseases caused by protozoa and helminths: human perspective and experimental models

The gamut of host immune responses and immunopathology in parasitic diseases caused by protozoa and helminths: human perspective and experimental models

Protozoan impact on bacterial biofilm formation

Protozoan impact on bacterial biofilm formation Confocal laser scanning microscopy in combination with digital image analysis was used to assess the impact of protozoa on bacterial colonisation of surfaces. Bacterial biofilms were developed from activated sludge in microscope flow cells and were exposed to the grazing pressure of protozoa. The protozoan community from healthy activated sludge and a culture of flagellate Bodo saltans were used as grazers. Experiments comprised 48-h incubations in 3 treatment variants: bacteria with protozoa, bacteria with protozoa added after some time and bacteria without protozoa. When necessary, the elimination of protozoa from the inoculum was carried out with cycloheximide and NiSO4. Experiments demonstrated that protozoa from healthy activated sludge initially disturbed the biofilm development but later they could stimulate its growth. Similar results could be established in the experiment with Bodo saltans (inoculum: 1000 cells/ml), however differences were not statistically significant. The finding that protozoa support biofilm development during specific stages may be relevant for biofilm studies with mixed environmental biofilm communities.

The effect of fluctuations in rumen pH on protozoa populations in rumen fluid as determined by real-time polymerase chain reaction

Ruminal ciliated protozoa are similar to bacteria in that their numbers increase in response to increased substrate availability. Moderate increases in grain intake result in large increases in the numbers of ciliated protozoa (Dennis et al., 1983). In contrast, high-or all grain diets have variable effects, including total elimination of protozoa in some animals (Franzolin and Dehority, 1996). Ciliated protozoa are believed to be much more sensitive than bacteria to fluctuations and reductions in ruminal pH; hence, ruminal pH is a critical factor in the maintenance of ciliated protozoa in the rumen. The objective of the present experiment was to investigate the effect of fluctuation in ruminal pH on the population of protozoa in rumen fluid.

Changes in methane emission and rumen fermentation parameters induced by refaunation in sheep

Elimination of protozoa or defaunation is known to reduce methane emission by ruminants. However, the long-term efficacy of this practice is not well documented. In this work methane and other end products of fermentation were monitored in five adult, rumen-cannulated wethers that had been kept defaunated for two years (Def1) and successively refaunated (Fau, 12 weeks) and defaunated (Def2) during a 6-month-long experiment. Methane was measured for periods of 4 days at about 4-weekly intervals using the SF6 tracer technique, and rumen content samples were taken regularly throughout the experiment. Refaunation was performed by single administration of a mixed protozoal inoculum (103 cells). A noticeable protozoal population was observed at 12 days after inoculation, which was followed by an exponential increase that peaked at 12 ± 3 × 105 cells/mL rumen fluid at 4 weeks and decreased thereafter to 8 ± 4 × 105 cells/mL at the end of the 12-week Fau period. Production of methane, which was 33 ± 8 L/animal.day in Def1, increased (P < 0.05) up to 42 ± 5 L at the end of the Fau period and dropped back at the end of Def2 to 35 ± 7 L (Def1 v. Def2, P > 0.05). Even though protozoal numbers were comparable to conventional animals 20 days after inoculation, the increase in methane production was observed later, at 8 weeks, suggesting that protozoa are not the only microbial factor favouring methanogenesis and that the ecosystem needs a relatively long adaptation time following protozoal introduction to optimise this function. The presence of protozoa did not affect total volatile fatty acids and acetate concentration in the rumen but increased butyrate, while decreasing propionate concentration (Fau v. Def1, Def2, P < 0.05). These results show that the decrease in methane emissions induced by defaunation in sheep was stable for a period of up to 2 years. In the absence of protozoa, methane decreased by ~20% in both short- and long-term defaunated animals.

Archaeal community structure diversity in the rumen of faunated and defaunated sheep

Elimination of protozoa from the rumen is usually accompanied by a decrease in methane production. However, the possible changes brought about by defaunation upon the structure of the methanogenic population are not known. Archaeal communities of rumen samples from 2 faunated (F), 2 recently defaunated (3 months, D−), and 2 long-term defaunated (+ 1 year, D+) sheep were profiled by PCR-denaturing gradient gel electrophoresis (DGGE) using 16S rDNA primers. Dendrogram analysis of the whole densitometric curves separated F and D+ in different clusters. Samples from D− animals did not show high similarity and were not separated into an independent cluster although they tended to be placed at an intermediate distance between F and D+. Principal components analysis (PCA) also confirmed these results. Bands explaining most of the differences in PCA could be correlated ( P < 0.05) to the presence/absence of protozoa. As measured by the Shannon index (H) based on DGGE operational taxonomic units, D+ populations had a lower diversity than F or D− populations ( P < 0.05). Shifts in the archaeal community structure of the rumen in the presence or absence of protozoa were identified. Population changes that follow defaunation seem to develop slowly as evidenced by the differences between recent and long-term defaunated animals.

Necrotrophic Growth of Legionella pneumophila

This study examined whether Legionella pneumophila is able to thrive on heat-killed microbial cells (necrotrophy) present in biofilms or heat-treated water systems. Quantification by means of plate counting, real-time PCR, and flow cytometry demonstrated necrotrophic growth of L. pneumophila in water after 96 h, when at least 100 dead cells are available to one L. pneumophila cell. Compared to the starting concentration of L. pneumophila, the maximum observed necrotrophic growth was 1.89 log units for real-time PCR and 1.49 log units for plate counting. The average growth was 1.57 +/- 0.32 log units (n = 5) for real-time PCR and 1.14 +/- 0.35 log units (n = 5) for plate counting. Viability staining and flow cytometry showed that the fraction of living cells in the L. pneumophila population rose from the initial 54% to 82% after 96 h. Growth was measured on heat-killed Pseudomonas putida, Escherichia coli, Acanthamoeba castellanii, Saccharomyces boulardii, and a biofilm sample. Gram-positive organisms did not result in significant growth of L. pneumophila, probably due to their robust cell wall structure. Although necrotrophy showed lower growth yields compared to replication within protozoan hosts, these findings indicate that it may be of major importance in the environmental persistence of L. pneumophila. Techniques aimed at the elimination of protozoa or biofilm from water systems will not necessarily result in a subsequent removal of L. pneumophila unless the formation of dead microbial cells is minimized.

Digestion in defaunated and refaunated sheep fed soybean oil hydrolysate or crushed toasted soybeans

Defaunated then refaunated sheep were given diets containing soyabean oil hydrolysate (SOH: 70 g/day) or an equivalent amount of lipids administered as crushed toasted soyabeans (TSB). Defaunation increased molar percentage of propionate in the rumen, while butyrate decreased. SOH caused a similar effect in both the defaunated and refaunated rumen, while the effect on acetate proportions was variable. Protozoal counts were lower after feeding SOH. Crushed toasted soyabeans had a minor effect on rumen fermentation pattern. Rumen digestibility of organic matter was decreased by both defaunation and SOH feeding, with a concomitant shift in digestion to the lower intestinal tract. Total tract digestibility was not affected. Both treatments increased nonammonia N flows at the duodenum, but this was only significant with defaunation. Total tract digestion of N remained almost constant. Defaunation resulted in more microbial protein reaching the duodenum. Except for the TSB diet, total lipid leaving the rumen equalled intake. Total tract digestibility of total lipid was much higher with SOH and TSB than with controls. Defaunation almost doubled microbial growth efficiency and this value tended to increase by SOH feeding. The decrease of protozoal count or even elimination of protozoa after lipid feeding could not entirely explain the change in rumen metabolism, as additional changes in defaunated sheep were shown.

A Simple Method for the Elimination of Protozoa from Mixed Cultures of Bacteria

A Simple Method for the Elimination of Protozoa from Mixed Cultures of Bacteria