The ability of non-bacteriocin producing Streptococcus bovis strains to bind and transfer bovicin HC5 to other sensitive bacteria

Streptococcus bovis HC5 produces a broad spectrum lantibiotic (bovicin HC5), but S. bovis JB1 does not have antimicrobial activity. Preliminary experiments revealed an anomaly. When S. bovis JB1 cells were washed in stationary phase S. bovis HC5 cell-free culture supernatant, the S. bovis JB1 cells were subsequently able to inhibit hyper-ammonia producing ruminal bacteria (Clostridium sticklandii, Clostridium aminophilum and Peptostreptococcus anaerobius). Other non-bacteriocin producing S. bovis strains also had the ability to bind and transfer semi-purified bovicin HC5. Bovicin HC5 that was bound to S. bovis JB1 was much more resistant to Pronase E than cell-free bovicin HC5, but it could be inactivated if the incubation period was 24 h. Acidic NaCl treatment (100 mM, pH 2.0) liberates half of the bovicin HC5 from S. bovis HC5, but it did not prevent bovicin HC5 from binding to S. bovis JB1. Acidic NaCl liberated some bovicin HC5 from S. bovis JB1, but the decrease in activity was only 2-fold. Bovicin HC5 is a positively charged peptide, and the ability of S. bovis JB1 to bind bovicin HC5 could be inhibited by either calcium or magnesium (100 mM). Acidic NaCl-treated S. bovis JB1 cells were unable to accumulate potassium, but they were still able to bind bovicin HC5 and prevent potassium accumulation by untreated S. bovis JB1 cells. Based on these results, bovicin HC5 bound to S. bovis JB1 cells still acts as a pore-forming lantibiotic.     

Production of bacteriocins by Streptococcus bovis strains from Australian ruminants

Aims: To examine the prevalence of bacteriocin production in Streptococcus bovis isolates from Australian ruminants and the feasibility of industrial production of bacteriocin. Methods and Results: Streptococcus bovis strains were tested for production of bacteriocin‐like inhibitory substances (BLIS) by antagonism assay against Lactococcus lactis. BLIS production was associated with source animal location (i.e. proximity of other bacteriocin‐positive source animals) rather than ruminant species/breed or diet. One bacteriocin showing strong inhibitory activity (Sb15) was isolated and examined. Protein sequence, stability and activity spectrum of this bovicin were very similar to bovicin HC5. Production could be increased through serial culturing, and increased productivity could be partially maintained during cold storage of cultures. Conclusions: BLIS production is geographically widely distributed in Eastern Australia, and it appears that the bacteriocin⁺ trait is maintained in animals at the same location. The HC5‐like bacteriocin, originally identified in North America, is also found in Australia. Production of bacteriocin can be increased through serial culturing. Significance and Impact of the Study: The HC5‐like bacteriocins appear to have a broad global distribution. Serial culturing may provide a route towards commercial manufacturing for use in industrial applications, and purified bacteriocin from S. bovis Sb15 could potentially be used to prevent food spoilage or as a feed additive to promote growth in ruminant species.     

Factors affecting the activity of bovicin HC5, a bacteriocin from Streptococcus bovis HC5: release, stability and binding to target bacteria

AIMS: To determine the factors affecting the release, stability and binding of bovicin HC5 to sensitive bacteria. METHODS AND RESULTS: Stationary phase Streptococcus bovis HC5 cultures had little cell-free bovicin HC5 activity until the final pH was <5.0, and even more bacteriocin was released by treatment with acidic NaCl (pH 2.0, 100 mmol l(-1)). Cultures grown with Tween 80 had more cell-free bovicin HC5 than untreated controls, but this nonionic detergent enhanced activity rather than release. Bovicin HC5 binding to S. bovis JB1 (a susceptible strain) was greater at pH values <6.0. Bovicin HC5 bound other sensitive Gram-positive bacteria, but not Gram-negative species. Cultures retained most of their activity for 35 days, but only if the final pH was <5.6. If the final pH was >5.6, peptidases destroyed much of the activity. CONCLUSIONS: Bovicin HC5 remains cell associated until the culture pH is <5.0, but it can be easily dissociated from the cell surface by acidic NaCl. It is highly stable in acidic environments and only binds sensitive bacteria at pH values <6.0. SIGNIFICANCE AND IMPACT OF THE STUDY: Streptococcus bovis HC5 does not have generally regarded as safe status. However, bovicin HC5 has a broad spectrum of activity and sensitive bacteria do not become resistant. Based on these results, bovicin HC5 may be a useful bacteriocin model.     

Nisin Resistance of Streptococcus bovis

The growth of Streptococcus bovis JB1 was initially inhibited by nisin (1 μM), and nisin caused a more than 3-log decrease in viability. However, some of the cells survived, and these nisin-resistant cells grew as rapidly as untreated ones. To see if the nisin resistance was merely a selection, nisin-sensitive cells were obtained from agar plates lacking nisin. Results indicated that virtually any nisin-sensitive cell could become nisin-resistant if the ratio of nisin to cells was not too high and the incubation period was long enough. Isolates obtained from the rumen were initially nisin sensitive, but they also developed nisin resistance. Nisin-resistant cultures remained nisin resistant even if nisin was not present, but competition studies indicated that nisin-sensitive cells could eventually displace the resistant ones if nisin was not present. Nisin-sensitive, glucose-energized cells lost virtually all of their intracellular potassium if 1 μM nisin was added, but resistant cells retained potassium even after addition of 10 μM nisin. Nisin-resistant cells were less hydrophobic and more lysozyme-resistant than nisin-sensitive cells. Because the nisin-resistant cells bound less cytochrome c, it appeared that nisin was being excluded by a net positive (i.e., less negative) charge. Nisin-resistant cells had more lipoteichoic acid than nisin-sensitive cells, and deesterified lipoteichoic acids from nisin-resistant cells migrated more slowly through a polyacrylamide gel than those from nisin-sensitive cells. These results indicated that lipoteichoic acids could be modified to increase the resistance of S. bovis to nisin. S. bovis JB1 cultures were still sensitive to monensin, tetracycline, vancomycin, and bacitracin, but ampicillin resistance was 1,000-fold greater.     

Effect of pH on the activity of bovicin HC5, a bacteriocin from Streptococcus bovis HC5

The bacteriocin, bovicin HC5, catalyzed potassium efflux from Streptococcus bovis JB1, and this activity was highly pH dependent. When the pH was near neutral, glucose-energized cells were not affected by bovicin HC5, but the intracellular steady-state concentration of potassium decreased at acidic pH values. The idea that pH was affecting bovicin HC5 binding was supported by the observation that acidic pH also enhanced the efflux of potassium from non-energized cells that had been loaded with potassium. The relationship between bovicin HC5 concentration and potassium depletion was a saturation function, but cooperativity plots indicated that the binding of one bovicin molecule to the cell membrane facilitated the binding of another.     

Factors Affecting the Antibacterial Activity of the Ruminal Bacterium,Streptococcus bovis HC5

Streptococcus bovis HC5 inhibits a variety of S. bovis strains and other Gram-positive bacteria, but factors affecting this activity had not been defined. Batch culture studies indicated that S. bovis HC5 did not inhibit S. bovis JB1 (a non-bacteriocin-producing strain) until glucose was depleted and cells were entering stationary phase, but slow-dilution-rate, continuous cultures (0.2 h⁻¹) had as much antibacterial activity as stationary-phase batch cultures. Because the activity of continuous cultures (0.2–1.2 h⁻¹) was inversely related to the glucose consumption rate, it appeared that the antibacterial activity was being catabolite repressed by glucose. When the pH of continuous cultures (0.2 h⁻¹) was decreased from 6.7 to 5.4, antibacterial activity doubled, but this activity declined at pH values less than 5.0. Continuous cultures (0.2 h⁻¹) that had only ammonia as a nitrogen source had antibacterial activity, and large amounts of Trypticase (10 mg ml⁻¹) caused only a 2.0-fold decline in the amount of HC5 cell-associated protein that was needed to prevent S. bovis JB1 growth. Because S. bovis HC5 was able to produce antibacterial activity over a wide range of culture conditions, there is an increased likelihood that this activity could have commercial application. Received: 6 February 2002 / Accepted: 27 March 2002     

The bacteriocins of ruminal bacteria and their potential as an alternative to antibiotics

Beef cattle have been fed ionophores and other antibiotics for more than 20 years to decrease ruminal fermentation losses (e.g methane and ammonia) and increase feed efficiency, and these improvements have been explained by an inhibition of gram-positive ruminal bacteria. Ionophores are not used to treat human disease, but there has been an increased perception that antibiotics should not be used as feed additives. Some bacteria produce small peptides (bacteriocins) that inhibit gram-positive bacteria. In vitro experiments indicated that the bacteriocin, nisin, and the ionophore, monensin, had similar effects on ruminal fermentation. However, preliminary results indicated that mixed ruminal bacteria degraded nisin, and the ruminal bacterium, Streptococcus bovis, became highly nisin-resistant. A variety of ruminal bacteria produce bacteriocins, and bacteriocin production has, in some cases, been correlated with changes in ruminal ecology. Some ruminal bacteriocins are as potent as nisin in vitro, and resistance can be circumvented. Based on these results, ruminal bacteriocins may provide an alternative to antibiotics in cattle rations.     

Characteristics and identification of bacteriocins produced by Lactococcus lactis subsp. lactis 194-K

The Lactococcus lactis subsp. lactis 194-K strain has been established to be able to produce two bacteriocins, one of which was identified as the known lantibiotic nisin A, and the other 194-D bacteriocin represents a polypeptide with a 2589-Da molecular mass and comprises 20 amino acid residues. Both bacteriocins were produced in varying proportions in all of the studied culture media, which support the growth of the producer. Depending on the cultivation medium, the nisin A content was 380- to 1123-fold lower in the 194-K stain culture broth than that of the 194-D peptide. In comparision to nisin A Bacteriocin 194-D possessed a wide range of antibacterial activity and suppressed the growth of both Gram-positive and Gram-negative bacteria. An optimal medium for 194-D bacteriocin synthesis was shown to be a fermentation medium which contained yeast extract, casein hydrolysate, and potassium phosphate. The biosynthesis of bacteriocin 194-D by the 194-K strain in these media occurred parallel to producer growth, and its maximal accumulation in the culture broth was observed at14–20 h of the strain’s growth.     

The effect of carbon and nitrogen sources on bovicin HC5 production by Streptococcus bovis HC5

Aims:  To investigate the effect of media composition and agroindustrial residues on bovicin HC5 production by Streptococcus bovis HC5.
Methods and Results:  Batch cultures of S. bovis HC5 were grown in basal medium containing different carbon and nitrogen sources. The activity of cell-free and cell-associated bovicin HC5 was determined in culture supernatants and acidic extracts obtained from cell pellets, respectively. Streptococcus bovis HC5 produced bovicin using a variety of carbon and nitrogen sources. The highest specific activity was obtained in media containing 16 g l⁻¹ of glucose, after 16 h of incubation. The peak in cell-free and cell-associated bovicin HC5 activity was detected when S. bovis HC5 cultures reached stationary phase. The bovicin HC5 specific activity and bacterial cell mass increased approximately 3-fold when yeast extract and trypticase (0·5 and 1·0 g l⁻¹, respectively) were added together to the basal medium. Streptococcus bovis HC5 cultures produced bovicin HC5 in cheese whey and sugar cane juice and maximal volumetric productivity was obtained after 12 h of incubation.
Conclusions:  Streptococcus bovis HC5 is a versatile lactic acid bacterium that can utilize several carbon and nitrogen sources for bovicin HC5 production. This bacterium could be a useful model to study bacteriocin production in the rumen ecosystem.
Significance and Impact of the Study:  The use of agroindustrial residues as carbon sources could have an economical impact on bovicin HC5 production. To our knowledge, this is the first report to show the use of sugar cane juice for bacteriocin production by lactic acid bacteria.     

Effects of the Oral Administration of Viable and Heat-Killed Streptococcus bovis HC5 Cells to Pre-Sensitized BALB/c Mice

Antimicrobial peptides have been suggested as an alternative to classical antibiotics in livestock production and bacteriocin-producing bacteria could be added to animal feeds to deliver bacteriocins in the gastrointestinal (GI) tract of ruminant and monogastric animals. In this study, viable (V) and heat-killed (HK) Streptococcus bovis HC5 cells were orally administered to pre-sensitized mice in order to assess the effects of a bacteriocin-producing bacteria on histological parameters and the immune response of the GI tract of monogastric animals. The administration of V and HK S. bovis HC5 cells during 58 days to BALB/c mice did not affect weight gain, but an increase in gut permeability was detected in animals receiving the HK cells. Viable and heat killed cells caused similar morphological alterations in the GI tract of the animals, but the most prominent effects were detected in the small intestine. The oral administration of S. bovis HC5 also influenced cytokine production in the small intestine, and the immune-mediated activity differed between V and HK cells. The relative expression of IL-12 and INF-γ was significantly higher in the small intestine of mice treated with V cells, while an increase in IL-5, IL-13 and TNF-α expression was only detected in mice treated with HK cells. Considering that even under a condition of severe challenge (pre-sensitization followed by daily exposure to the same bacterial immunogen) the general health of the animals was maintained, it appears that oral administration of S. bovis HC5 cells could be a useful route to deliver bacteriocin in the GI tract of livestock animals.     

Effect of bovicin HC5 on growth and spore germination of Bacillus cereus and Bacillus thuringiensis isolated from spoiled mango pulp

AIMS: To use bovicin HC5 to inhibit predominant bacteria isolated from spoiled mango pulp. METHODS AND RESULTS: Bovicin HC5 and nisin were added to brain heart infusion (BHI) medium (40-160 AU ml(-1)) or mango pulp (100 AU ml(-1)) and the growth of Bacillus cereus and Bacillus thuringiensis was monitored. Cultures treated with bovicin HC5 or nisin showed longer lag phases and grew slower in BHI medium. Bovicin HC5 and nisin were bactericidal and showed higher activity in mango pulp at acidic pH values. To determine the effect on spore germination and D values, mango pulp containing bovicin HC5 was inoculated with 10(6) and 10(9) spores per ml(-1), respectively, from each strain tested. Bovicin HC5 reduced the outgrowth of spores from B. cereus and B. thuringiensis, but thermal sensitivity was not affected. CONCLUSIONS: Bovicin HC5 was bactericidal against B. cereus and B. thuringiensis isolated from spoiled mango pulp. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacillus cereus and B. thuringiensis had not been previously isolated from spoiled mango pulp and bovicin HC5 has the potential to inhibit such bacteria in fruit pulps.     

Bovicin HC5 inhibits wasteful amino acid degradation by mixed ruminal bacteria in vitro

Streptococcus bovis HC5 produces a broad spectrum lantibiotic (bovicin HC5) that inhibits pure cultures of hyper ammonia-producing bacteria (HAB). Experiments were preformed to see if: (1) S. bovis HC5 cells could inhibit the deamination of amino acids by mixed ruminal bacteria taken directly from a cow, (2) semi-purified bovicin was as effective as S. bovis HC5 cells, and 3) semi-purified and the feed additive monensin were affecting the same types of ammonia-producing ruminal bacteria. Because purified and semi-purified bovicin HC5 was as effective as S. bovis HC5 cells, it appeared that bovicin HC5 was penetrating the cell membranes of HAB before it could be degraded by peptidases and proteinases. Mixed ruminal bacteria that were successively transferred and enriched nine times with trypticase did not become significantly more resistant to either bovicin HC5 (50 AU mL⁻¹) or monensin (5 μM), and amplified rDNA restriction analysis indicated that bovicin HC5 and monensin appeared to be selecting against the same types of bacteria.     

Bacterial competition between a bacteriocin-producing and a bacteriocin-negative strain of Streptococcus bovis in batch and continuous culture

A bacteriocin-producing Streptococcus bovis strain (HC5) outcompeted a sensitive strain (JB1) before it reached stationary phase (pH 6.4), even though it grew 10% slower and cell-free bovicin HC5 could not yet be detected. The success of bacteriocin-negative S. bovis isolates was enhanced by the presence of another sensitive bacterium (Clostridium sticklandii SR). PCR based on repetitive DNA sequences indicated that S. bovis HC5 was not simply transferring bacteriocin genes to S. bovis JB1. When the two S. bovis strains were coinoculated into minimal medium, bacteriocin-negative isolates predominated, and this effect could be explained by the longer lag time (0.5 vs. 1.5 h) of S. bovis HC5. If the glucose concentration of the minimal medium was increased from 2 to 7 mg mL(-1), the effect of lag time was diminished and bacteriocin-producing isolates once again dominated the coculture. When the competition was examined in continuous culture, it became apparent that batch culture inocula were never able to displace a strain that had already reached steady state, even if the inoculum was large. This result indicated that bacterial selection for substrate affinity was even more important than bacteriocin production.     

Nisin resistance of Streptococcus bovis

The growth of Streptococcus bovis JB1 was initially inhibited by nisin (1 microM), and nisin caused a more than 3-log decrease in viability. However, some of the cells survived, and these nisin-resistant cells grew as rapidly as untreated ones. To see if the nisin resistance was merely a selection, nisin-sensitive cells were obtained from agar plates lacking nisin. Results indicated that virtually any nisin-sensitive cell could become nisin-resistant if the ratio of nisin to cells was not too high and the incubation period was long enough. Isolates obtained from the rumen were initially nisin sensitive, but they also developed nisin resistance. Nisin-resistant cultures remained nisin resistant even if nisin was not present, but competition studies indicated that nisin-sensitive cells could eventually displace the resistant ones if nisin was not present. Nisin-sensitive, glucose-energized cells lost virtually all of their intracellular potassium if 1 microM nisin was added, but resistant cells retained potassium even after addition of 10 microM nisin. Nisin-resistant cells were less hydrophobic and more lysozyme-resistant than nisin-sensitive cells. Because the nisin-resistant cells bound less cytochrome c, it appeared that nisin was being excluded by a net positive (i.e., less negative) charge. Nisin-resistant cells had more lipoteichoic acid than nisin-sensitive cells, and deesterified lipoteichoic acids from nisin-resistant cells migrated more slowly through a polyacrylamide gel than those from nisin-sensitive cells. These results indicated that lipoteichoic acids could be modified to increase the resistance of S. bovis to nisin. S. bovis JB1 cultures were still sensitive to monensin, tetracycline, vancomycin, and bacitracin, but ampicillin resistance was 1,000-fold greater.     

Combined Effect of Bacteriocins on the Survival of Various Listeria Species in Broth and Meat System

The antilisterial efficiency of three bacteriocins from lactic acid bacteria, lactocin 705 (produced by L. casei CRL705, 17000 AU/ml), enterocin CRL35 (produced by E. faecium CRL35, 17000 AU/ml), and nisin (2000 IU/ml), was tested in broth, individually and in combination against Listeria monocytogenes and Listeria innocua. Both Listeria species showed an initial decrease in viable counts followed by the regrowth of the survivors after 1 h in the presence of each bacteriocin. A greater antilisterial effect was observed when the bacteriocins were combined in pairs, maximal inhibition being reached when nisin was involved. When a mix of the three bacteriocins was used, no survivors were observed after 24 h of incubation. Similar results were obtained when the bacteriocin combinations were tested in a meat system, indicating that the use of more than one LAB bacteriocin in combination may be effective in preventing the spontaneous emergence of a bacteriocin-resistant Listeria population. Received: 17 March 2000 / Accepted: 26 June 2000     

Use of bacteriocinogenic lactic acid bacteria to inhibit spontaneous nisin-resistant mutants of Listeria monocytogenes Scott A

Nisin is a bacteriocin with a broad antibacterial spectrum including strains of Listeria monocytogenes . Populations of L. monocytogenes , however, frequently contain spontaneous nisin-resistant mutants. When a culture of L. monocytogenes Scott A was exposed to nisin concentrations between 10 and 500 IU ml⁻¹, the initial decrease in viable numbers was followed by regrowth of survivors to nisin. Nisin-resistant mutants of L. monocytogenes Scott A were isolated after a single exposure to nisin at 100 IU ml⁻¹ and were shown to be sensitive to the non-nisin bacteriocins, sakacin A and enterocin B, produced by Lactobacillus sake Lb 706 and Enterococcus faecium BFE 900, respectively. The regrowth of L. monocytogenes Scott A following the initial decrease due to exposure to nisin was prevented by nisin-resistant Lact. sake Lb 706–1a and to a somewhat lesser extent, by Ent. faecium BFE 900–6a. Listerial cells surviving nisin action were thus inhibited by the bacteriocin-producing strains that might be used as starter or protective cultures in foods. Growth of a nisin-resistant mutant of L. monocytogenes Scott A (Li3) was also suppressed by the bacteriocinogenic cultures. Use of nisin in combination with a starter culture producing a non-nisin antilisterial bacteriocin may therefore prevent the emergence of nisin-resistant mutants of L. monocytogenes .     

Lactococcal membrane-permeabilizing antimicrobial peptides

A number of lactococcal antimicrobial peptides, bacteriocins have been discovered and characterized. Since Lactococcus spp. are generally regarded as safe bacteria, their bacteriocins are expected for various application uses. Most of lactococcal bacteriocins exert antimicrobial activity via membrane permeabilization. The most studied and prominent bacteriocin, nisin A is characterized in the high activity and has been utilized as food preservatives for more than half a century. Recently, other lactococcal bacteriocins such as lacticin Q were found to have distinguished features for further applications as the next generation to nisin.     

Growth,acid production and bacteriocin production by probiotic candidates under simulated colonic conditions

Aims

The aim of this study is to evaluate the capacity of three bacteriocin producers, namely Lactococcus lactis subsp. lactis biovar diacetylactis UL719 (nisin Z producer), L. lactis ATCC 11454 (nisin A producer) and Pediococcus acidilactici UL5 (pediocin PA‐1 producer), and to grow and produce their active bacteriocins in Macfarlane broth, which mimics the nutrient composition encountered in the human large intestine.

Methods and Results

The three bacteriocin‐producing strains were grown in Macfarlane broth and in De Man–Rogosa–Sharpe (MRS) broth. For each strain, the bacterial count, pH drop and production of organic acids and bacteriocins were measured for different period of time. The ability of the probiotic candidates to inhibit Listeria ivanovii HPB 28 in co‐culture in Macfarlane broth was also examined. Lactococcus lactis subsp. lactis biovar diacetylactis UL719, L. lactis ATCC 11454 and Ped. acidilactici UL5 were able to grow and produce their bacteriocins in MRS broth and in Macfarlane broth. Each of the three candidates inhibited L. ivanovii HPB 28, and this inhibition activity was correlated with bacteriocin production. The role of bacteriocin production in the inhibition of L. ivanovii in Macfarlane broth was confirmed for Ped. acidilactici UL5 using a pediocin nonproducer mutant.

Conclusions

The data provide some evidence that these bacteria can produce bacteriocins in a complex medium with carbon source similar to those found in the colon.

Significance and Impact of the Study

This study demonstrates the capacity of lactic acid bacteria to produce their bacteriocins in a medium simulating the nutrient composition of the large intestine.     

The Ability of “Low G + C Gram-Positive” Ruminal Bacteria to Resist Monensin and Counteract Potassium Depletion

Gram-negative ruminal bacteria with an outer membrane are generally more resistant to the feed additive, monensin, than Gram-positive species, but some bacteria can adapt and increase their resistance. 16S rRNA sequencing indicates that a variety of ruminal bacteria are found in the “low G + C Gram-positive group,” but some of these bacteria are monensin resistant and were previously described as Gram-negative species (e.g., Selenomonas ruminantium and Megasphaera elsdenii). The activity of monensin can be assayed by its ability to cause potassium loss, and results indicated that the amount of monensin needed to catalyze half maximal potassium depletion (K_d) from low G + C gram-positive ruminal bacteria varied by as much as 130-fold. The K_d values for Butyrivibrio fibrisolvens 49, Streptococcus bovis JB1, Clostridium aminophilum F, S. ruminantium HD4, and M. elsdenii B159 were 10, 65, 100, 1020, and 1330 nM monensin, respectively. B. fibrisolvens was very sensitive to monensin, and it did not adapt. S. bovis and C. aminophilum cultures that were transferred repeatedly with sub-lethal doses of monensin had higher K_d values than unadapted cultures, but the K_d was always less than 800 nM. S. ruminantium and M. elsdenii cells were highly resistant (K_d > 1000 nM), and this resistance could be explained by the ability of these low G + C Gram-positive bacteria to synthesize outer membranes. Received: 14 May 1999 / Accepted: 24 June 1999     

Deoxyribonuclease Activity in Selenomonas ruminantium, Streptococcus bovis, and Bacteroides ovatus

Six Selenomonas ruminantium strains (132c, JW13, SRK1, 179f, 5521c1, and 5934e), Streptococcus bovis JB1, and Bacteroides ovatus V975 were examined for nuclease activity as well as the ability to utilize nucleic acids, ribose, and 2-deoxyribose. Nuclease activity was detected in sonicated cells and culture supernatants for all bacteria except S. ruminantium JW13 and 179f sonicated cells. S. ruminantium strains were able to utilize several deoxyribonucleosides, while S. bovis JB1 and B. ovatus V975 showed little or no growth on all deoxyribonucleosides. When S. ruminantium strains 5934e, 132c, JW13, and SRK1 were incubated in medium that contained 15 mm ribose, the major end products were acetate, propionate, and lactate. S. ruminantium 5521c1 and S. bovis JB1 did not grow on ribose, and none of the S. ruminantium strains or S. bovis JB1 grew on 15 mm 2-deoxyribose. In contrast, B. ovatus V975 was able to grow on ribose and 2-deoxyribose. In conclusion, all S. ruminantium strains, S. bovis JB1, and B. ovatus V975 had nuclease activity. However, not all bacteria were able to utilize deoxyribonucleosides, ribose, or 2-deoxyribose. Received: 9 February 2000 / Accepted: 27 March 2000