Streptococcus bovis endocarditis

A case is described of bacterial endocarditis caused by Lancefield group D Streptococcus bovis. Because of its sensitivity to the less toxic antibiotics such as penicillin, the importance of laboratory differentiation from the more resistant enterococci is emphasized. Treatment in this case was complicated by penicillin allergy and cardiac failure. The condition finally responded to clindamycin therapy and aortic valve replacement.     

A gene-targeting suicide vector for Streptococcus bovis

J.D. BROOKER, D.K. LUM, A.M. THOMSON AND H.M. WARD. 1995. A gene-targeting suicide vector for Streptococcus bovis has been constructed using the Escherichia coli/Streptococcus shuttle plasmid, pMU1328, and a region derived from the broad host-range, Gram-positive transposon, Tn916. This suicide plasmid replicates autonomously in E. coli , but not in Strep, bovis or Strep, bovis Tn916. Under positive selection, the plasmid was shown to integrate into Strep, bovis Tn916 chromosomal DNA at a frequency of 3 × 10^-8cell^-1and was stably maintained for at least 100 generations in the absence of selection. This is the first report of a recombination system in ruminal bacteria. The ability to target genes, knock out specific functions or introduce novel genes into these micro-organisms will allow ruminal species to be manipulated and may eventually lead to improved animal 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.     

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.     

Metabolism of the reserve polysaccharide of Streptococcus mitis: Properties of a transglucosylase

1. A transglucosylase has been separated from cell extracts of Streptococcus mitis, and has been partially purified by chromatography on DEAE-cellulose. 2. The transglucosylase was present in the six strains of Streptococcus mitis that were examined, and the activity of the enzyme was the same whether the cells had grown on glucose or on maltose. Four of the strains could store intracellular iodophilic polysaccharide when grown on high concentrations of glucose or maltose (1%), but none of the strains stored polysaccharide during growth on 0·1% glucose. The activity of transglucosylase in cell extracts was the same whether or not the cells had stored polysaccharide. 3. The transglucosylase degrades amylose in the presence of a suitable acceptor, transferring one or more glucosyl residues from the non-reducing end of the donor to the non-reducing end of the acceptor. With [¹⁴C]glucose as acceptor the maltodextrins produced were labelled in the reducing glucose unit only. 4. The enzyme can synthesize higher maltodextrins from maltose and maltotriose. Maltotetraose is disproportionated to give products of sufficient chain length to give a stain with iodine. 5. The action pattern of S. mitis during the degradation of synthetic amylose was shown to be intermediate between the single-chain and multi-chain mechanism.     

A note on the pectinolytic enzyme of Streptococcus bovis

A pectinolytic strain of Streptococcus bovis isolated from the bovine rumen produced an endopolygalacturonate lyase (EC 4.2.2.2). The principal decomposition products of pectin were unsaturated methyl tetra- and tri-galacturonates.     

A note on the pectinolytic enzyme of Streptococcus bovis

W ojciechowicz , M. & Z iolecki , A. 1984. A note on the pectinolytic enzyme of Streptococcus bovis. Journal of Applied Bacteriology 56 , 515–518.
A pectinolytic strain of Streptococcus bovis isolated from the bovine rumen produced an endopolygalacturonate lyase (EC 4.2.2.2). The principal decomposition products of pectin were unsaturated methyl tetra- and tri-galacturonates.     

Deoxyribonuclease activity in Streptococcus bovis

Deoxyribonuclease activity was tested with lambda bacteriophage DNA as a substrate in three Streptococcus bovis strains isolated from the rumen of sheep and cow. Non-specific nuclease activity was detected in the cell extract of Strep, bovis BM 114. Specific endonuclease activity was detected in the cell extract of the strain Strep. bovis II/I, isolated from the rumen of a sheep. A rapid technique is proposed for the detection of endonuclease activity of rumen bacteria.     

Arginine Biosynthesis by Streptococcus bovis

The pathway of arginine biosynthesis in Streptococcus bovis was studied by radioactive tracer techniques. Cells were grown anaerobically with (14)CO(2) in a synthetic medium containing NH(4) (+) as the sole nitrogen source except for the trace present in nitrogen-containing vitamins. The protein fraction isolated from the labeled cells was acid-hydrolyzed, and (14)C-arginine was isolated from the protein hydrolysate by ion-exchange chromatography. The carboxyl carbon of the isolated arginine was removed with arginine decarboxylase, and the guanidino carbon was removed by simultaneous arginase-urease degradation. By manometric measurement and liquid scintillation counting of the CO(2) released by enzymatic degradation, 50% of the label was found in the carboxyl carbon and 50% in the guanidino carbon. Specific radioactivity determinations indicated that growth on (14)CO(2) resulted in twice as much label in arginine as with aspartate, glutamate, or lysine. These results are consistent with a glutamate --> ornithine --> citrulline pathway of arginine biosynthesis in S. bovis and provide further evidence for the synthesis of glutamate via the tricarboxylic acid cycle reactions from citrate through alpha-ketoglutarate.     

Characterization of Streptococcus bovis bacteriophages.

About 25 Streptococcus bovis bacteriophages were isolated from abattoir wastes, bovine rumen fluid, and lysogenic strains of S. bovis. Eight phages were selected and characterized by morphology, stability, rate of adsorption, single-step growth curve, serum neutralization, and antigenic relationship. Two distinct morphological phage types were found, one of which has not been previously reported for group D streptococci.     

SbvI restriction endonuclease from Streptococcus bovis

Restriction endonuclease Sbv I, an isoschizomer of Hae III, has been isolated from rumen amylolytic bacterium Streptococcus bovis II/1. Sbv I was purified from cell extract by phosphocellulose chromatography and heparin-Sepharose chromatography. The recognition sequence of Sbv I was identified by digestion of pBR322, pUC9 and Λ-DNA and comparing the cleavage patterns obtained with computer-derived data. Sbv I recognizes the 4-bp palindrome, 5'-GGCC-3' and cleaves DNA after the second G in the sequence, producing blunt ends.     

A Simple Test for Differentiating Streptococcus bovis from other Streptococci

S ummary . Streptococcus bovis grew in acid media, which are normally inhibitory for this organism, when incubated in an atmosphere containing 5% (v/v) CO₂ or if the CO₂ produced by the organism itself was prevented from escaping from the media. Since no other streptococcus grew in acid media under these conditions, this finding enables Strep. bovis to be differentiated from other streptococci by a simple test.     

Identification of intracellular amylase activity in Streptococcus bovis and Streptococcus salivarius

The ruminal bacterium Streptococcus bovis has been demonstrated to produce an extracellular amylase activity. We previously reported on the cloning of a gene from S. bovis encoding for what was initially believed to be the extracellular amylase. DNA sequence analyses indicated that the amylase produced by the cloned gene did not match the N-terminus amino acid sequence of the purified extracellular amylase and contained no apparent leader sequence for secretion. Analyses of crude extracts demonstrated the presence of an intracellular amylase in S. bovis JB1 that differed in molecular weight (56,000) from that of the extracellular amylase (70,000). The 56,000 molecular weight amylase was identical to the amylase produced by Escherichia coli containing the cloned amylase gene. Low levels of intracellular amylase activity were also detected in other strains of S. bovis and also Streptococcus salivarius. Introduction of the plasmid pVA838 containing the cloned amylase gene into S. bovis and S. sanguis resulted in enhanced intracellular amylase production by both organisms. The amylase gene has been sequenced, and analysis of the deduced amino acid sequence for the amylase indicates a high degree of similarity with secreted amylases from Bacillus species.Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Transformation of Streptococcus bovis protoplasts by plasmid DNA

M. MAREKOVÁ, V. KMET' AND P. JAVORSKÝ. 1996. The transformation and subsequent regeneration of ruminal strain Streptococcus bovis AO24/85 protoplasts by plasmid DNA was studied. The best stabilizer for regeneration of protoplasted cells was 5% sucrose in the regeneration medium and in the agar plates. Optimal concentration of polyethylene glycol 6000 in the transformation medium was 25% for both plasmids tested. Addition of Ca²⁺ and Mg²⁺ ions (2.5 mmol l^-1) to the transformation medium increased the proportion of regenerated cells. Transformation frequencies were 3 times 10³ transformants per μg of pNZ12 and 2.4 times 10² per μg of pJK108, respectively.     

A Selective Medium for the Enumeration of Streptococcus bovis by Membrane Filtration

A new selective medium (membrane-bovis agar) for the detection and enumeration of Streptococcus bovis is described. It has been successfully used to quantify this organism in polluted waters, sewage and faeces of humans and farm animals. This medium is based on the ability of Strep. bovis to utilize ammonium sulphate as its sole source of nitrogen. Streptococcus faecalis, Strep. faecium, Strep. equinus, Strep. salivarius. Strep. mitis and other bacteria commonly found in water, sewage and faeces are completely inhibited.
Streptococcus bovis appear to be the predominant faecal streptococci in the faeces of farm animals and absent in the faeces of humans. A total of 541 characteristic colonies (on m-BA), isolated from various sources were identified to species level. Over 97% proved to be Strep. bovis. Therefore, routine confirmatory tests on colonies growing on this medium would appear to be unnecessary.     

Pigment production in chemostat cultures of Streptococcus bovis

Summary Streptococcus bovis 2B formed bright red cell clumps in glucose-limited defined medium under certain nonsteady state growth conditions. Scanning electron micrographs showed that clumped cells were more rounded than those from complex medium. Clumped cells appeared to be bound to one another at the cell surface and there was no sign of a polysaccharide matrix. Freeze fractured cells showed that the inner membrane particle distribution was different in the clumped cells from fast growing cells in complex or defined medium. Clumping is potentially a mechanism to decrease transport by reducing the cell surface area. It appears to be a nonsteady state phenomenon, occurring in situations leading to unbalanced growth.     

Protoplast Formation and Regeneration of Streptococcus bovis Cells

The simultaneous use of hen egg lysozyme and mutanolysin, N-acetylmuramidase SG, showed synergistic effects on the lytic action and more effectiveness for protoplast formation of Streptococcus bovis IFO 12058. The frequency of regeneration reached 100% after 7 days of incubation under the improved conditions and by a method in which protoplasts were overlaid with the agar medium layer.