Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed degradation and methane formation by ruminants rely on metabolic interactions between rumen microbes and affect ruminant productivity. Rumen and camelid foregut microbial community composition was determined in 742 samples from 32 animal species and 35 countries, to estimate if this was influenced by diet, host species, or geography. Similar bacteria and archaea dominated in nearly all samples, while protozoal communities were more variable. The dominant bacteria are poorly characterised, but the methanogenic archaea are better known and highly conserved across the world. This universality and limited diversity could make it possible to mitigate methane emissions by developing strategies that target the few dominant methanogens. Differences in microbial community compositions were predominantly attributable to diet, with the host being less influential. There were few strong co-occurrence patterns between microbes, suggesting that major metabolic interactions are non-selective rather than specific.

Brucella abortus is a facultative intracellular bacterium capable of surviving inside professional and nonprofessional phagocytes. The microorganism remains in membrane-bound compartments that in several cell types resemble modified endoplasmic reticulum structures. To monitor the intracellular transport of B. abortus in macrophages, the kinetics of fusion of phagosomes with preformed lysosomes labeled with colloidal gold particles was observed by electron microscopy. The results indicated that phagosomes containing live B. abortus were reluctant to fuse with lysosomes. Furthermore, newly endocytosed material was not incorporated into these phagosomes. These observations indicate that the bacteria strongly affect the normal maturation process of macrophage phagosomes. However, after overnight incubation, a significant percentage of the microorganisms were found in large phagosomes containing gold particles, resembling phagolysosomes. Most of the Brucella bacteria present in phagolysosomes were not morphologically altered, suggesting that they can also resist the harsh conditions prevalent in this compartment. About 50% colocalization of B. abortus with LysoSensor, a weak base that accumulates in acidic compartments, was observed, indicating that the B. abortus bacteria do not prevent phagosome acidification. In contrast to what has been described for HeLa cells, only a minor percentage of the microorganisms were found in compartments labeled with monodansylcadaverine, a marker for autophagosomes, and with DiOC6 (3,3-dihexyloxacarbocyanine iodide), a marker for the endoplasmic reticulum. These results indicate that B. abortus bacteria alter phagosome maturation in macrophages. However, acidification does occur in these phagosomes, and some of them can eventually mature to phagolysosomes.The facultative intracellular parasite Brucella abortus causes abortion and infertility in cattle and undulant fever in humans. The bacterium is endemic in many underdeveloped countries and responsible for large economic losses and chronic infections in human beings (30). Brucella infects its hosts through mucosae and wounds and initially is incorporated into professional phagocytes where it survives and reproduces (14). Afterwards, the bacterium infects several types of nonprofessional phagocytic cells including those of endocardium, brain, joints, and bones. Brucella has a special tropism for reproductive organs, causing a high rate of abortion in pregnant animals (28).The intracellular survival of Brucella has been documented for several cell types. According to multiple observations, B. abortus is incorporated into phagosomes and remains in membrane-bound compartments until the host cell dies. In nonprofessional phagocytes, Brucella is located in structures that resemble the endoplasmic reticulum (ER) (6). Recent evidence indicates that Brucella is transported through the autophagic pathway before accumulating in the ER (22, 23).Macrophages are particularly important for the survival and spreading of Brucella during infection ...

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We studied the presence of botulinum toxin-producing clostridia in 2,009 soil samples from five geographical regions of Argentina. The prevalence was 23.5%, and the distribution was not homogeneous among the regions. We observed a great multiplicity of serological types and a higher prevalence in nonvirgin soils than in virgin soils.The geographical distribution of botulinum toxin-producing clostridia (BTPC) (7) has been extensively studied in Europe, Asia, and North America (1,2,4,5,8,9,10,11,12,13,15,16,18,19,20,21,23,24,25,26). However, our knowledge concerning the presence of these anaerobes in South America is very restricted. In this study our principal aim was to examine the prevalence and distribution of BTPC in soils of Argentina.We examined 2,009 soil samples from Argentina. Because of the vast the territory and the climate and geographical variations, this country was divided into five regions ( Fig. 1 and Table 1). Soil samples were obtained and processed from 1964 until 2002. In each case the time between collection and examination was less than 2 days. Each sample was collected from a 100-cm 2 area by using a sterile metal spoon and then was transferred to a sterile receptacle and stored at room temperature until examination. Soils were classified into two categories: virgin and nonvirgin. Virgin soils were defined as soils that still were in their natural state and had not been used or changed by people. Nonvirgin soils were defined as soils that had been changed by people (cultivated, urbanized, and industrialized soils). Samples were processed by diluting 25 g of soil in 50 ml of a saline solution (0.15 M NaCl). Two aliquots were taken after 40 min of resting. One aliquot was immediately inoculated into chopped-meat medium (6). The other aliquot was subjected to a heat shock (80°C, 10 min) and later was inoculated into chopped-meat medium. After incubation for 5 days at 31°C, broth media were centrifuged at 12,000 ϫ g for 10 min at 4°C, and 0.5 ml was inoculated in duplicate intraperitoneally into mice. Mice were observed for 96 h for characteristic botulinal signs and death (14). Cultures without signs of proteolysis were treated by mixing equal volumes of the culture supernatant and 1% trypsin (1:250; Difco), followed by incubation at 37°C for 1 h. Toxic cultures were cultivated in solid media with 1.5% and 4.0% agar (0.4% meat extract, 1.0% glucose, 4.0% Proteose Peptone, 0.5% NaCl, 1.5% or 4.0% agar [pH 7.2]) and egg yolk agar (3). They were incubated for up to 24, 48, and 72 h, respectively, at 34°C in BBL jars with an atmosphere containing 80% N 2 , 10% CO 2 , and 10% H 2 . Selected colonies were transferred to chopped-meat medium and incubated for 4 days at 31°C. The presence of botulinum toxin was investigated in each of these cultures, as described previously. Toxic broth media were cultivated in solid media to ensure that the cultures were pure. Genera were identified by using gram-positive, strictly anaerobic, and sporulated bacilli. Species were not identified. Strains were cultivate...

Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed degradation and methane formation by ruminants rely on metabolic interactions between rumen microbes and affect ruminant productivity. Rumen and camelid foregut microbial community composition was determined in 742 samples from 32 animal species and 35 countries, to estimate if this was influenced by diet, host species, or geography. Similar bacteria and archaea dominated in nearly all samples, while protozoal communities were more variable. The dominant bacteria are poorly characterised, but the methanogenic archaea are better known and highly conserved across the world. This universality and limited diversity could make it possible to mitigate methane emissions by developing strategies that target the few dominant methanogens. Differences in microbial community compositions were predominantly attributable to diet, with the host being less influential. There were few strong co-occurrence patterns between microbes, suggesting that major metabolic interactions are non-selective rather than specific.

We isolated and identified functional groups of bacteria in the rumen of Creole goats involved in ruminal fermentation of native forage shrubs. The functional bacterial groups were evaluated by comparing the total viable, total anaerobic, cellulolytic, hemicellulolytic, and amylolytic bacterial counts in the samples taken from fistulated goats fed native forage diet (Atriplex lampa and Prosopis flexuosa). Alfalfa hay and corn were used as control diet. The roll tubes method increased the possibility of isolating and 16S rDNA gene sequencing allowed definitive identification of bacterial species involved in the ruminal fermentation. The starch and fiber contents of the diets influenced the number of total anaerobic bacteria and fibrolytic and amylolytic functional groups. Pseudobutyrivibrio ruminis and Pseudobutyrivibrio xylanivorans were the main species isolated and identified. The identification of bacterial strains involved in the rumen fermentation helps to explain the ability of these animals to digest fiber plant cell wall contained in native forage species.

This work investigated the changes of the rumen microbiome of goats switched from a forage to a concentrate diet with special attention to anaerobic fungi (AF). Female goats were fed an alfalfa hay (AH) diet (0% grain; n = 4) for 20 days and were then abruptly shifted to a high-grain (HG) diet (40% corn grain, 60% AH; n = 4) and treated for another 10 days. Rumen content samples were collected from the cannulated animals at the end of each diet period (day 20 and 30). The microbiome structure was studied using high-throughput sequencing for bacteria, archaea (16S rRNA gene) and fungi (ITS2), accompanied by qPCR for each group. To further elucidate unclassified AF, clone library analyses were performed on the ITS1 spacer region. Rumen pH was significantly lower in HG diet fed goats, but did not induce subacute ruminal acidosis. HG diet altered prokaryotic communities, with a significant increase of Bacteroidetes and a decrease of Firmicutes. On the genus level Prevotella 1 was significantly boosted. Methanobrevibacter and Methanosphaera were the most abundant archaea regardless of the diet and HG induced a significant augmentation of unclassified Thermoplasmatales. For anaerobic fungi, HG triggered a considerable rise in Feramyces observed with both ITS markers, while a decline of Tahromyces was detected by ITS2 and decrease of Joblinomyces by ITS1 only. The uncultured BlackRhino group revealed by ITS1 and further elucidated in one sample by LSU analysis, formed a considerable part of the AF community of goats fed both diets. Results strongly indicate that the rumen ecosystem still acts as a source for novel microorganisms and unexplored microbial interactions and that initial rumen microbiota of the host animal considerably influences the reaction pattern upon diet change.

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