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Red swamp crayfish (Procambarus clarkii) like to eat aquatic plants. The intestinal microorganism plays an important role in cellulose degradation and utilization. Isolating bacteria which can degrade cellulose from the intestines of P. clarkii can provide a theoretical basis for the development of probiotics in forage for P. clarkii. Three selective media including carboxymethyl-cellulose, microcrystalline cellulose, and cellobiose were used in plate cultures for 48h and then dyed with Congo red. It was found that 5 strains produced hydrolytic rings on 3 culture media at 48h. Based on the results of 16S rRNA molecular analysis, strains C, E, G, H, and M were identified as Citrobacter sp., Staphylococcus sp., Acinetobacter johnsonii, Shewanella sp., and Aeromonas caviae, respectively. Specifically, Staphylococcus sp. exhibited the strongest capacity for the degradation of cellulose. Shewanella sp. showed the strongest degradation capacity for cellobiose. Acinetobacter johnsonii and Shewanella sp. can degrade cellulose and are expected to be used as probiotic feed for P. clarkii. This study can provide a theoretical basis for the healthy culture of P. clarkii.

The necessity of reducing enzyme production costs and their wide use in several industrial sectors, have increased the interest on agro-industrial wastes valorization as substrates for the obtention of these bioproducts. Given that agricultural wastes are both a source of cellulose and cellulolytic microorganisms, the purpose of this study was the selection of previously isolated cellulolytic bacteria from wastes generated in marketplaces and, the evaluation of media formulated from this waste. 11 bacterial strains were grown in Mandel’s broth for 72 hours evaluating their cellulolytic activity at 30 and 50 ºC. To formulate the culture media, the cellulose, nitrogen and total organic carbon content in corn cob leaves and legume seed pods collected in a marketplace was determined. Three types of media were made using cellulose, sourced from waste, supplemented with peptone, ammonium sulfate and urea: the last three added as Nitrogen source. Medium A was formulated with chopped and dehydrated wastes. Medium B had the same treatment than medium A plus a liquefy step. Medium C was made with un-dehydrated and liquefied waste. From the 5 selected cellulolytic strains, C6M2 was cultured at 37 ºC on each of the three media and the enzyme activity was monitored for 96 hours of fermentation. Cellulase production was achieved in media A and B. Medium A presented higher production (19,82 ± 3,0 U/mL). On the other hand, no cellulolytic activity was evidenced in medium C. The corn cob leaves and legume seed pods, chopped and dehydrated, allow the cellulase production using the bacterium strain C6M2., La necesidad de reducir los costos de producción de las enzimas y su amplia utilización en diferentes sectores industriales, ha incrementado el interés en la valorización de residuos agroindustriales como sustratos para la obtención de estos bioproductos. Los residuos agrícolas son una fuente tanto de celulosa como de microorganismos productores de celulasas, por lo que este estudio tuvo como propósito la selección de bacterias celulolíticas aisladas previamente de residuos generados en plazas de mercado y la evaluación de medios formulados a partir de estos. 11 cepas bacterianas fueron cultivadas en caldo Mandels durante 72 horas, evaluando su actividad celulolítica a 30 y 50 ºC. Para la formulación de medios de cultivo se determinó el contenido de celulosa, nitrógeno y carbono orgánico total de los ameros de mazorca y vainas de leguminosas recolectados en una plaza de mercado. Se elaboraron tres medios de cultivo utilizando los residuos como fuente de celulosa y suplementándolos con peptona, sulfato de amonio y urea como fuente de nitrógeno. El medio A se formuló con residuos troceados y deshidratados, en el medio B estos tuvieron el mismo tratamiento adicionando un paso de licuado y para el medio C se utilizaron residuos licuados sin deshidratar. De las 5 cepas celulolíticas seleccionadas, C6M2 fue cultivada a 37 ºC en los tres medios y la actividad enzimática fue monitoreada durante las 96 horas de fermentación. En los medios A y B se evidenció la producción de celulasas, siendo A el que presentó una mayor actividad (19,82 ± 3,0 U/mL), mientras que en el medio C no se evidenció actividad celulolítica. En conclusión, la cepa bacteriana seleccionada C6M2 es capaz de producir celulasas en medios de cultivo formulados con ameros de mazorca y vainas de leguminosas troceados y deshidratados.

The review is devoted cellulolytic microorganisms that provide biodegradation of cellulose. The questions of taxonomy, general properties. Attention is paid to comparison of aerobic, anaerobic and facultative anaerobic cellulolytic organisms, their morphology-functional features., Обзор посвящен целлюлолитическим микроорганизмам, которые обеспечивают биодеградацию целлюлозы. Рассматриваются вопросы их таксономии, общих свойств. Уделено внимание сравнению аэробных, анаэробных и факультативно анаэробных целлюлолитических микроорганизмов, их морфо-функциональным особенностям., Огляд присвячений целюлолітичним мікроорганізмам, які забезпечують біодеградацію целюлози. Розглядаються питання їх таксономії, загальних властивостей. Приділено увагу порівнянню аеробних, анаеробних та факультативно анаеробних целюлолітичних мікроорганізмів, їх морфо- функціональним особливостям.

The objective of the current study was to assess how closely batch cultures (BC) of rumen microorganisms can mimic the dietary differences in fermentation characteristics found in the rumen, and to analyse changes in bacterial diversity over the in vitro incubation period. Four ruminally and duodenally cannulated sheep were fed four diets having forage : concentrate ratios (FCR) of 70 : 30 or 30 : 70, with either alfalfa hay or grass hay as forage. Rumen fluid from each sheep was used to inoculate BC containing the same diet fed to the donor sheep, and the main rumen fermentation parameters were determined after 24 h of incubation. There were differences between BC and sheep in the magnitude of most measured parameters, but BC detected differences among diets due to forage type similar to those found in sheep. In contrast, BC did not reproduce the dietary differences due to FCR found in sheep for pH, degradability of neutral detergent fibre and total volatile fatty acid (VFA) concentrations. There were differences between systems in the magnitude of most determined parameters and BC showed higher pH values and NH3-N concentrations, but lower fibre degradability and VFA and lactate concentrations compared with sheep. There were significant relationships between in vivo and in vitro values for molar proportions of acetate, propionate and butyrate, and the acetate : propionate ratio. The automated ribosomal intergenic spacer analysis (ARISA) of 16S ribosomal deoxyribonucleic acid showed that FCR had no effect on bacterial diversity either in the sheep rumen fluid used as inoculum (IN) or in BC samples. In contrast, bacterial diversity was greater with alfalfa hay diets than those with grass hay in the IN, but was unaffected by forage type in the BC. Similarity index between the bacterial communities in the inocula and those in the BC ranged from 67.2 to 74.7%, and was unaffected by diet characteristics. Bacterial diversity was lower in BC than in the inocula with 14 pe

The rumen microbial ecosystem is known for its biomass-degrading and methane-producing phenotype. Fermentation of recalcitrant plant material, comprised of a multitude of interwoven fibers, necessitates the synergistic activity of diverse microbial taxonomic groups that inhabit the anaerobic rumen ecosystem. Although interspecies hydrogen (H2) transfer, a process during which bacterially generated H2 is transferred to methanogenic Archaea, has obtained significant attention over the last decades, the temporal variation of the different taxa involved in in situ biomass-degradation, H2 transfer and the methanogenesis process remains to be established. Here we investigated the temporal succession of microbial taxa and its effect on fiber composition during rumen incubation using 16S rRNA amplicon sequencing. Switchgrass filled nylon bags were placed in the rumen of a cannulated cow and collected at nine time points for DNA extraction and 16S pyrotag profiling. The microbial community colonizing the air-dried and non-incubated (0 h) switchgrass was dominated by members of the Bacilli (recruiting 63% of the pyrotag reads). During in situ incubation of the switchgrass, two major shifts in the community composition were observed: Bacilli were replaced within 30 min by members belonging to the Bacteroidia and Clostridia, which recruited 34 and 25% of the 16S rRNA reads generated, respectively. A second significant shift was observed after 16 h of rumen incubation, when members of the Spirochaetes and Fibrobacteria classes became more abundant in the fiber-adherent community. During the first 30 min of rumen incubation ~13% of the switchgrass dry matter was degraded, whereas little biomass degradation appeared to have occurred between 30 min and 4 h after the switchgrass was placed in the rumen. Interestingly, methanogenic members of the Euryarchaeota (i.e., Methanobacteria) increased up to 3-fold during this period of reduced biomass-degradation, with peak abundance just be

The rumen microbial ecosystem is known for its biomass-degrading and methane-producing phenotype. Fermentation of recalcitrant plant material, comprised of a multitude of interwoven fibers, necessitates the synergistic activity of diverse microbial taxonomic groups that inhabit the anaerobic rumen ecosystem. Although interspecies hydrogen (H2) transfer, a process during which bacterially generated H2 is transferred to methanogenic Archaea, has obtained significant attention over the last decades, the temporal variation of the different taxa involved in in situ biomass-degradation, H2 transfer and the methanogenesis process remains to be established. Here we investigated the temporal succession of microbial taxa and its effect on fiber composition during rumen incubation using 16S rRNA amplicon sequencing. Switchgrass filled nylon bags were placed in the rumen of a cannulated cow and collected at nine time points for DNA extraction and 16S pyrotag profiling. The microbial community colonizing the air-dried and non-incubated (0 h) switchgrass was dominated by members of the Bacilli (recruiting 63% of the pyrotag reads). During in situ incubation of the switchgrass, two major shifts in the community composition were observed: Bacilli were replaced within 30 min by members belonging to the Bacteroidia and Clostridia, which recruited 34 and 25% of the 16S rRNA reads generated, respectively. A second significant shift was observed after 16 h of rumen incubation, when members of the Spirochaetes and Fibrobacteria classes became more abundant in the fiber-adherent community. During the first 30 min of rumen incubation ~13% of the switchgrass dry matter was degraded, whereas little biomass degradation appeared to have occurred between 30 min and 4 h after the switchgrass was placed in the rumen. Interestingly, methanogenic members of the Euryarchaeota (i.e., Methanobacteria) increased up to 3-fold during this period of reduced biomass-degradation, with peak abundance just be

The rumen microbial ecosystem is known for its biomass-degrading and methane-producing phenotype. Fermentation of recalcitrant plant material, comprised of a multitude of interwoven fibers, necessitates the synergistic activity of diverse microbial taxonomic groups that inhabit the anaerobic rumen ecosystem. Although interspecies hydrogen (H2) transfer, a process during which bacterially generated H2 is transferred to methanogenic Archaea, has obtained significant attention over the last decades, the temporal variation of the different taxa involved in in situ biomass-degradation, H2 transfer and the methanogenesis process remains to be established. Here we investigated the temporal succession of microbial taxa and its effect on fiber composition during rumen incubation using 16S rRNA amplicon sequencing. Switchgrass filled nylon bags were placed in the rumen of a cannulated cow and collected at nine time points for DNA extraction and 16S pyrotag profiling. The microbial community colonizing the air-dried and non-incubated (0 h) switchgrass was dominated by members of the Bacilli (recruiting 63% of the pyrotag reads). During in situ incubation of the switchgrass, two major shifts in the community composition were observed: Bacilli were replaced within 30 min by members belonging to the Bacteroidia and Clostridia, which recruited 34 and 25% of the 16S rRNA reads generated, respectively. A second significant shift was observed after 16 h of rumen incubation, when members of the Spirochaetes and Fibrobacteria classes became more abundant in the fiber-adherent community. During the first 30 min of rumen incubation ~13% of the switchgrass dry matter was degraded, whereas little biomass degradation appeared to have occurred between 30 min and 4 h after the switchgrass was placed in the rumen. Interestingly, methanogenic members of the Euryarchaeota (i.e., Methanobacteria) increased up to 3-fold during this period of reduced biomass-degradation, with peak abundance just be

Four ruminally cannulated sheep were used in a crossover design to assess the postprandial changes of fiber-degrading microbes in the solid phase of the rumen of sheep fed 2 high-forage diets. The diets had forage: concentrate ratio of 70: 30 (DM basis) and either alfalfa (Medicago sativa) hay (AL) or grass hay (GR) as forage (FOR). Sheep were fed twice daily, and samples from solid rumen digesta were taken at 0, 4, and 8 h after the morning feeding. Postprandial changes of DNA concentrations of all determined microbial populations were similar for the 2 diets. Samples taken at 4 h after feeding had lesser (P < 0.05) concentrations of total bacterial DNA determined with real-time PCR and bacterial diversity and greater (P < 0.05) protozoal DNA concentrations, relative abundance of fungal, Fibrobacter succinogenes, Ruminococcus flavefaciens, and Ruminococcus albus DNA compared with those taken at 0 and 8 h. No effect (P = 0.41 to 0.76) of FOR was detected either on concentrations of bacterial and protozoal DNA or the relative abundance of the 2 Ruminococcus DNA, but GR diet promoted greater (P < 0.001) relative abundance of F. succinogenes and fungal DNA compared with AL diet. Fibrobacter succinogenes was the most abundant (P < 0.05) of the 3 cellulolytic bacteria for both diets, with no differences (P < 0.05) between the 2 Ruminococcus species. Rumen pH and carboxymethylcellulase, Avicelase, and amylase activities were not affected (P = 0.15 to 0.69) by FOR, but xylanase activity was greater (P = 0.01) for GR diet. The influence of FOR on microbial communities in ruminal solid digesta was more evident in the first hours after feeding than at later times after feeding, which highlights the influence of sampling time when investigating dietary effects on rumen function and microbial populations.

In this study, the technique of cryopreservation in liquid nitrogen to preserve native isolates of the fibrolytic bacteria Fibrobacter succinogenes was standardized. The technique efficiency was evaluated by establishing the bacterium viability during one year. The Mac-Farland scale, widely used to estimate aerobic bacterial populations, was validated by the roll tube technique (R2=0.95). Two native F. succinogenes strains, C7 and C9, were used. These strains were obtained from cattle fed on Brachiaria decumbens in the eastern lowlands of Colombia. Fifteen days after the initiation of the cryopreservation process, a reduction in the number of viable bacteria (CFU ml-1) was registered (C7 from 9.25 x 108 to 6.15 x 108 and C9 from 12.51 x 108 to. 9.26 x 108). However, the bacterial populations did not present differences in subsequent samplings (C7=6.13 – 6.16X108, C9=9.26 – 9.35X108 CFU ml-1, range over a year). Results indicated that the tandardized cryopreservation technique is an effective and easy procedure to preserve ruminal bacteria, which would be a very useful tool to create a germplasm bank of Colombian ruminal anaerobic microorganisms. The criopreservation technique, and the MacFarland scale have an advantage over other methods of preserving bacteria and methods of estimating populations of bacteria by active cultures. The procedures used in this research are reliable and economical techniques using minimal storage spaces and laboratory resources., En el presente trabajo se estandarizó una técnica de criopreservación en nitrógeno líquido, usando como crioprotector dimetil sulfóxido al 5%, para la preservación de aislados nativos bacterianos de Fibrobacter succinogenes. El respectivo protocolo de criopreservación se evaluó determinando la viabilidad bacteriana por el transcurso de un año. La escala de MacFarland, ampliamente conocida en la estimación de poblaciones bacterianas aerobias, fue validada como técnica de estimación de bacterias anaerobias, usando la técnica de conteo bacteriano por roll-tube (R2 = 0.95). Se utilizaron dos aislados nativos, C7 y C9, de Fibrobacter succinogenes, obtenidos del rumen de bovinos en pastoreo de Brachiaria decumbens, en los Llanos Orientales de Colombia. Quince días después de la exposición de los cultivos al proceso de criopreservación, se apreció una reducción en el número de bacterias viables con relación a la población inicial de cada uno de los aislados (C7 = 9.25 x 108 UFCml-1 vs. 6.15 x 108 UFCml-1 y C9 = 12.51 x 108 UFCml-1 vs. 9.26 x 108 UFCml-1). Sin embargo, no se presentaron diferencias en la población de bacterias viables en los muestreos posteriores (C7 = 6.13 – 6.16 x 108; C9 = 9.26 – 9.35 x 108 UFCml-1). Esta técnica permite mantener la viabilidad bacteriana y puede considerarse como un procedimiento eficiente y de fácil aplicación para la preservación de bacterias ruminales. Además, constituye una herramienta fundamental para el establecimiento de bancos de germoplasma de microorganismos anaerobios ruminales en Colombia. El uso conjunto de las técnicas de criopreservación y la escala de MacFarland, posee ventajas sobre los métodos de preservación y estimación de poblaciones por cultivos activos, por su confiabilidad, eficiencia y bajo costo.

In this study, the technique of cryopreservation in liquid nitrogen to preserve native isolates of the fibrolytic bacteria Fibrobacter succinogenes was standardized. The technique efficiency was evaluated by establishing the bacterium viability during one year. The Mac-Farland scale, widely used to estimate aerobic bacterial populations, was validated by the roll tube technique (R2=0.95). Two native F. succinogenes strains, C7 and C9, were used. These strains were obtained from cattle fed on Brachiaria decumbens in the eastern lowlands of Colombia. Fifteen days after the initiation of the cryopreservation process, a reduction in the number of viable bacteria (CFU ml-1) was registered (C7 from 9.25 x 108 to 6.15 x 108 and C9 from 12.51 x 108 to. 9.26 x 108). However, the bacterial populations did not present differences in subsequent samplings (C7=6.13 – 6.16X108, C9=9.26 – 9.35X108 CFU ml-1, range over a year). Results indicated that the tandardized cryopreservation technique is an effective and easy procedure to preserve ruminal bacteria, which would be a very useful tool to create a germplasm bank of Colombian ruminal anaerobic microorganisms. The criopreservation technique, and the MacFarland scale have an advantage over other methods of preserving bacteria and methods of estimating populations of bacteria by active cultures. The procedures used in this research are reliable and economical techniques using minimal storage spaces and laboratory resources., En el presente trabajo se estandarizó una técnica de criopreservación en nitrógeno líquido, usando como crioprotector dimetil sulfóxido al 5%, para la preservación de aislados nativos bacterianos de Fibrobacter succinogenes. El respectivo protocolo de criopreservación se evaluó determinando la viabilidad bacteriana por el transcurso de un año. La escala de MacFarland, ampliamente conocida en la estimación de poblaciones bacterianas aerobias, fue validada como técnica de estimación de bacterias anaerobias, usando la técnica de conteo bacteriano por roll-tube (R2 = 0.95). Se utilizaron dos aislados nativos, C7 y C9, de Fibrobacter succinogenes, obtenidos del rumen de bovinos en pastoreo de Brachiaria decumbens, en los Llanos Orientales de Colombia. Quince días después de la exposición de los cultivos al proceso de criopreservación, se apreció una reducción en el número de bacterias viables con relación a la población inicial de cada uno de los aislados (C7 = 9.25 x 108 UFCml-1 vs. 6.15 x 108 UFCml-1 y C9 = 12.51 x 108 UFCml-1 vs. 9.26 x 108 UFCml-1). Sin embargo, no se presentaron diferencias en la población de bacterias viables en los muestreos posteriores (C7 = 6.13 – 6.16 x 108; C9 = 9.26 – 9.35 x 108 UFCml-1). Esta técnica permite mantener la viabilidad bacteriana y puede considerarse como un procedimiento eficiente y de fácil aplicación para la preservación de bacterias ruminales. Además, constituye una herramienta fundamental para el establecimiento de bancos de germoplasma de microorganismos anaerobios ruminales en Colombia. El uso conjunto de las técnicas de criopreservación y la escala de MacFarland, posee ventajas sobre los métodos de preservación y estimación de poblaciones por cultivos activos, por su confiabilidad, eficiencia y bajo costo.

The rumen bacterial strains Butyrivibrio fibrisolvens H17c, Fibrobacter succinogenes S85, Lachnospira multiparus 40, Ruminococcus albus 7 and R. flavefaciens FD-1 were compared individually and as a five-species mixture with a rumen inoculum for their ability to degrade lucerne (Medicago sativa L.) stem cell wall polysaccharides. Two maturity stages of lucerne (bud and full flower) were utilized as substrates and incubation periods of 24 and 96 h were employed. Lucerne stem substrates and fermentation residues were analysed for cell wall content and composition. Degradation of total cell wall polysaccharides and all polysaccharide fractions was greater for immature than for mature lucerne stems. The 96-h incubation resulted in significantly more degradation of all cell wall polysaccharides than did the 24-h incubation. The R. albus culture was able to degrade all cell wall polysaccharide fractions as well or better than any other culture, including the rumen inoculum. Co-culture of R. albus with the four other ruminal species did not improve degradation of any wall polysaccharides compared with R. albus alone. Microscopic examination indicated that R. albus and the five-species mixture appeared to degrade Lucerne tissues in thin sections to almost the same extent as did rumen fluid.

A Characterization study of rumen cellulolytic bacteria of cattle was conducted at the National Research Center "Tibaitatá" of Corpoica, located in a highland (2550 m.a.s.l) tropical ecosystem of Colombia. Five anaerobic strains of cellulolytic bacteria (F31, F32, F33, R38 and R39) were isolated from the rumen contents of cattle fed on raygrass (Lolium multiflorum) hay. Classification of the isolated rumen bacteria strains was accomplished by biochemical tests, carbohydrate fermentation patterns and morphological characterization, including transmission electron microscopy (TEM) of cell membrane and glycocalix. The isolated strains were: Fibrobacter succinogenes succinogenes (F31y F32), Fibrobacter succi nogenes elongata (F33), Ruminococcus albus (R38) and Ruminococcus flavefaciens (R39). Ruminococcus albus fermented more carbohydrate sources than Ruminococcus flavefaciens, however, both species fermented cellobiose, pectin and xilan Fibrobacter isolates did not ferment pentose sugar s. Six different types of morphology of the colony, sorne of them not reported previously, were observed in Fibrobacter isolates growing on agar-containing roll­ tubes. Ruminococcus species were identified as R. albus and R. fla vefaciens by differences in cell structure, size and distribution of the glycocalix. Ultrastructural studies confirmed the taxonomic status of isolated bacteria species. Isolated bacteria are the first entries to the reference rumen germplasm bank of cattle in Colombia. Enzymatic assays are being conducted to measure cellulolytic activity of the isolated strains., En el Centro Nacional de Investigaciones “Tibaitatá” de Corpoica, localizado en un ecosistema trópical a una altura de 2550 m.s.n.m, se adelantó un estudio para caracterizar la población de bacterias celulolíticas ruminales de bovinos. Cinco cepas de bacterias anaerobias celulolíticas fueron aisladas a partir del contenido ruminal de bovinos alimentados con heno de raigrás (Lolium multijlorum). Las pruebas bioquímicas, el patrón de fermentación de carbohidratos y la caracterización morfológica, incluyendo los estudios de microscopía electrónica de transmisión de la membrana celular y el glicocáliz, permitieron clasificar las cepas aisladas como: Fibrobacter succinogenes succinogenes (F31 y F32), Fibrobacter succinogenes elongata(F33), Ruminococcus albus (R38) y Ruminococcus flavefaciens (R39). La cepa de R. albus fermentó un mayor número de fuentes de carbono que la cepa de R. flavefaciens, pero ambas, fermentaron celobiosa, pectina y xilano. Ninguna de las dos subespecies de Fibrobacter aisladas fermentó pentosas. Las cepas de Fibrobacter presentaron morfologías de colonia en roll-tube de agar celobiosa, no repor­ tadas en la literatura. La apariencia, tamaño y distribución del glicocáliz en las células de las cepas del género Ruminococcus hicieron posible la diferenciación de sus dos espe­ cies R. albus y R. flavefaciens y la confirmación del status taxonómico de las otras cepas celulolíticas. Las cepas aisladas constituyen las primeras entradas al banco de germoplasma microbial de referencia para bovinos en Colombia. Actualmente se adelantan los estudios de actividad enzimática celulolítica de estas cepas.

A Characterization study of rumen cellulolytic bacteria of cattle was conducted at the National Research Center "Tibaitatá" of Corpoica, located in a highland (2550 m.a.s.l) tropical ecosystem of Colombia. Five anaerobic strains of cellulolytic bacteria (F31, F32, F33, R38 and R39) were isolated from the rumen contents of cattle fed on raygrass (Lolium multiflorum) hay. Classification of the isolated rumen bacteria strains was accomplished by biochemical tests, carbohydrate fermentation patterns and morphological characterization, including transmission electron microscopy (TEM) of cell membrane and glycocalix. The isolated strains were: Fibrobacter succinogenes succinogenes (F31y F32), Fibrobacter succi nogenes elongata (F33), Ruminococcus albus (R38) and Ruminococcus flavefaciens (R39). Ruminococcus albus fermented more carbohydrate sources than Ruminococcus flavefaciens, however, both species fermented cellobiose, pectin and xilan Fibrobacter isolates did not ferment pentose sugar s. Six different types of morphology of the colony, sorne of them not reported previously, were observed in Fibrobacter isolates growing on agar-containing roll­ tubes. Ruminococcus species were identified as R. albus and R. fla vefaciens by differences in cell structure, size and distribution of the glycocalix. Ultrastructural studies confirmed the taxonomic status of isolated bacteria species. Isolated bacteria are the first entries to the reference rumen germplasm bank of cattle in Colombia. Enzymatic assays are being conducted to measure cellulolytic activity of the isolated strains., En el Centro Nacional de Investigaciones “Tibaitatá” de Corpoica, localizado en un ecosistema trópical a una altura de 2550 m.s.n.m, se adelantó un estudio para caracterizar la población de bacterias celulolíticas ruminales de bovinos. Cinco cepas de bacterias anaerobias celulolíticas fueron aisladas a partir del contenido ruminal de bovinos alimentados con heno de raigrás (Lolium multijlorum). Las pruebas bioquímicas, el patrón de fermentación de carbohidratos y la caracterización morfológica, incluyendo los estudios de microscopía electrónica de transmisión de la membrana celular y el glicocáliz, permitieron clasificar las cepas aisladas como: Fibrobacter succinogenes succinogenes (F31 y F32), Fibrobacter succinogenes elongata(F33), Ruminococcus albus (R38) y Ruminococcus flavefaciens (R39). La cepa de R. albus fermentó un mayor número de fuentes de carbono que la cepa de R. flavefaciens, pero ambas, fermentaron celobiosa, pectina y xilano. Ninguna de las dos subespecies de Fibrobacter aisladas fermentó pentosas. Las cepas de Fibrobacter presentaron morfologías de colonia en roll-tube de agar celobiosa, no repor­ tadas en la literatura. La apariencia, tamaño y distribución del glicocáliz en las células de las cepas del género Ruminococcus hicieron posible la diferenciación de sus dos espe­ cies R. albus y R. flavefaciens y la confirmación del status taxonómico de las otras cepas celulolíticas. Las cepas aisladas constituyen las primeras entradas al banco de germoplasma microbial de referencia para bovinos en Colombia. Actualmente se adelantan los estudios de actividad enzimática celulolítica de estas cepas.