Highly divergent mitochondrion-related organelles in anaerobic parasitic protozoa.

The mitochondria have arisen as a consequence of endosymbiosis of an ancestral α-proteobacterium with a methane-producing archae. The main function of the canonical aerobic mitochondria include ATP generation via oxidative phosphorylation, heme and phospholipid synthesis, calcium homeostasis, programmed cell death, and the formation of iron-sulfur clusters. Under oxygen-restricted conditions, the mitochondrion has often undergone remarkable reductive alterations of its content and function, leading to the generation of mitochondrion-related organelles (MROs), such as mitosomes, hydrogenosomes, and mithochondrion-like organelles, which are found in a wide range of anaerobic/microaerophilic eukaryotes that include several medically important parasitic protists such as Entamoeba histolytica, Giardia intestinalis, Trichomonas vaginalis, Cryptosporidium parvum, Blastocystis hominis, and Encephalitozoon cuniculi, as well as free-living protists such as Sawyeria marylandensis, Neocallimastix patriciarum, and Mastigamoeba balamuthi. The transformation from canonical aerobic mitochondria to MROs apparently have occurred in independent lineages, and resulted in the diversity of their components and functions. Due to medical and veterinary importance of the MRO-possessing human- and animal-pathogenic protozoa, their genomic, transcriptomic, proteomic, and biochemical evidence has been accumulated. Detailed analyses of the constituents and functions of the MROs in such anaerobic pathogenic protozoa, which reside oxygen-deprived or oxygen-poor environments such as the mammalian intestine and the genital organs, should illuminate the current evolutionary status of the MROs in these organisms, and give insight to environmental constraints that drive the evolution of eukaryotes and their organelles. In this review, we summarize and discuss the diverse metabolic functions and protein transport systems of the MROs from anaerobic parasitic protozoa.

Effect of feeding isolates of anaerobic fungus Neocallimastix sp. CF 17 on growth rate and fibre digestion in buffalo calves.

In this investigation, the effects of feeding encapsulated cells (rhizomycelia and zoospores) of a fibrolytic isolate from an anaerobic fungus (Neocallimastix sp. CF 17) on nutrient digestion, ruminal fermentation, microbial populations, enzyme profile and growth performance were evaluated in buffaloes. In three in vitro studies, the true digestibility of wheat straw was increased after addition of CF 17 to buffalo rumen fluid (p < 0.05). In Exp. 1, three groups of six buffaloes each (initial BW [body weight] 148 +/- 12.0 kg) were allotted to three dosing regimes: Group 1 received 200 ml of liquid culture of Neocallimastix sp. CF 17 (about 10(6) TFU [thallus-forming units]/ml); Group 2 received an encapsulated culture of the same fungi prepared from 200 ml liquid culture; Group 3: received 200 ml of autoclaved culture (Control). The supplementations were given weekly for four weeks (on days 1,7, 14 and 21). During the dosing period, the average daily gain of Group 2 was higher than in the Control group (444 g/d compared with 264 g/d; p < 0.05). Furthermore, the digestibility of organic matter increased in Group 1 and 2 compared with the Control (64.8, 64.0 and 60.4% respectively; p < 0.05), resulting in an increase in the total digestible nutrient (TDN) percent of ration (p < 0.05). But these effects disappeared post-dosing. There were also an increase in concentration of volatile fatty acids, trichloroacetic acid precipitable N and number of fibrolytic microbes in the rumen during the dosing period (p < 0.05), but these effects declined post-dosing. Results of Exp 2., where the encapsulated culture was applied at intervals of 4 d or 8 d for 120 d, showed that a shorter dosing frequency did not improve growth performance or feed intake. However, independent of the dosing frequency the growth rate of both groups fed the encapsulated culture were about 20% higher than in the Control group (p < 0.05). The present study showed that encapsulated fungi have a high potential to be used as feed additive at the farmers' level and that weekly dosing can increase growth performance of wheat straw based diets.

Effects of aromatic amino acids, phenylacetate and phenylpropionate on fermentation of xylan by the rumen anaerobic fungi, Neocallimastix frontalis and Piromyces communis.

AIMS: Anaerobic fungi are important members of the fibrolytic community of the rumen. The aim of this study was to study their requirement for aromatic amino acids (AA) and related phenyl acids (phenylpropionic and phenylacetic acids) for optimal xylan fermentation. METHODS AND RESULTS: Neocallimastix frontalis RE1 and Piromyces communis P were grown in a defined medium containing oat spelts xylan as the sole energy source, plus one of the following N sources: ammonia; ammonia plus a complete mixture of 20 AA commonly found in protein; ammonia plus complete AA mixture minus aromatic AA; ammonia plus phenyl acids; ammonia plus complete AA mixture without aromatic AA plus phenyl acids. Both species grew in all the media, indicating no absolute requirement for AA. The complete AA mixture increased (P<0.05) acetate concentration by 18% and 15%, sugar utilization by 33% and 22% and microbial yield by about 22% and 15% in N. frontalis and P. communis, respectively, in comparison with the treatments that had ammonia as the only N source. Neither the supply of aromatic AA or phenol acids, nor their deletion from the complete AA mixture, affected the fermentation rate, products or yield of either species. CONCLUSIONS: AA were not essential for N. frontalis and P. communis, but their growth on xylan was stimulated. The effects could not be explained in terms of aromatic AA alone. SIGNIFICANCE AND IMPACT OF THE STUDY: Ruminant diets should contain sufficient protein to sustain optimal fibre digestion by ruminal fungi. Aromatic AA or phenyl acids alone cannot replace the complete AA mixture.