Effect of Canavanine from Alfalfa Seeds on the Population Biology of Bacillus cereus

Bacillus cereus UW85 suppresses diseases of alfalfa seedlings, although alfalfa seed exudate inhibits the growth of UW85 in culture (J. L. Milner, S. J. Raffel, B. J. Lethbridge, and J. Handelsman, Appl. Microbiol. Biotechnol. 43:685–691, 1995). In this study, we determined the chemical basis for and biological role of the inhibitory activity. All of the alfalfa germ plasm tested included seeds that released inhibitory material. We purified the inhibitory material from one alfalfa cultivar and identified it as canavanine, which was present in the cultivar Iroquois seed exudate at a concentration of 2 mg/g of seeds. Multiple lines of evidence suggested that canavanine activity accounted for all of the inhibitory activity. Both canavanine and seed exudate inhibited the growth of UW85 on minimal medium; growth inhibition by either canavanine or seed exudate was prevented by arginine, histidine, or lysine; and canavanine and crude seed exudate had the same spectrum of activity against B. cereus, Bacillus thuringiensis, and Vibrio cholerae. The B. cereus UW85 populations surrounding canavanine-exuding seeds were up to 100-fold smaller than the populations surrounding non-canavanine-exuding seeds, but canavanine did not affect the growth of UW85 on seed surfaces. The spermosphere populations of canavanine-resistant mutants of UW85 were larger than the spermosphere populations of UW85, but the mutants and UW85 were similar in spermoplane colonization. These results indicate that canavanine exuded from alfalfa seeds affects the population biology of B. cereus.     

Photosynthetic characterization of photoautotrophic cells cultured in a minimal medium

Photosynthetic properties of photoautotrophic suspensions cultured in a minimal growth medium have been evaluated to determine whether changes have occurred in ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity, phosphoenol-pyruvate (PEP) carboxylase activity, chlorophyll content, or culture growth. Five photoautotrophic lines Amaranthus powellii, Datura innoxia, Glycine max, Gossypium hirsutum, and a Nicotiana tabacum-Nicotiana glutinosa fusion hybrid were grown in a medium without organic carbon other than phytohormones, and without vitamins. These photoautotrophic lines had total Rubisco activities ranging from 85 to 266 micromoles CO₂ fixed per milligram chlorophyll hour⁻¹, with percent activation of Rubisco ranging from 16 to 53%. Inclusion of protease inhibitors in the homogenization buffer did not result in higher Rubisco activity. PEP carboxylase activity for cells cultured in minimal medium was found to range from 16 to 146 micromoles CO₂ per milligram chlorophyll hour⁻¹, with no higher activity in the C₄Amaranthus cells compared with PEP carboxylase activity in the C₃ species assayed. Rubisco-to-PEP carboxylase ratios ranged from 2.2 to 1 up to 9.4 to 1. Chlorophyll contents increased in all but the Nicotiana cell line, and all of the photoautotrophic culture lines were capable of growth in vitamin-free medium with the exception of SB-P, which requires thiamine.     

Phosphorylation by protein kinase C and the responsiveness of Mg2+-ATPase to Ca2+ of myofibrils isolated from stunned and non-stunned porcine myocardium

Previously we showed in an in situ porcine model that the thiadiazinone derivative [+]EMD 60263, a Ca²⁺ sensitizer without phosphodiesterase III inhibitory properties, increased contractility more profoundly in stunned than in non-stunned myocardium. This finding was consistent with the observed leftward shifts of the pCa²⁺/Mg²⁺-ATPase curves of isolated myofibrils induced by [+]EMD 60263. The aim of the present investigation was to study the possible involvement of protein kinase C in the mechanism of reduced Ca²⁺ responsiveness of myofilaments during stunning. No differences were observed in the maximal activity of the Ca²⁺-stimulated Mg²⁺-ATPase and in the pCa₅₀ of myofibrils isolated from non-stunned and stunned myocardium. After phosphorylation with [gamma-³²P]-ATP and excess of purified rat brain protein kinase C, the myofibrils were separated on sodiumdodecylsulphate-polyacrylamide gelectrophoresis and the³² P incorporation counted by the Molecular Imager. Ca²⁺/phosphatidylserine/sn-1,2 diolein-dependent³² P incorporation catalyzed by excess of purified rat brain protein kinase C in C-protein, TnT and TnI subunits did not show any differences between myofibrils from non-stunned and stunned myocardium. However, protein kinase C-induced phosphorylation of myofibrils isolated from ventricular myocardium of sham-operated pigs resulted in a marked leftward shift of the pCa₅₀ from 6.03 ± 0.04 to 6.44 ± 0.06 (p < 0.05), while porcine heart cyclic AMP-dependent protein kinase-induced phosphorylation resulted in an expected small rightward shift to 5.97, although statistical significance was not reached. Protein kinase C-induced phosphorylation also stimulated (80%) the maximal myofibrillar Mg²⁺-ATPase activity. [+]EMD 60263 (3 µM) produced a leftward shift of the myofibrillar pCa²⁺/Mg²⁺-ATPase curve which was unaffected by prior protein kinase C-induced phosphorylation. In conclusion, the findings with isolated myofibrils from myocardium of anaesthetized open-chest pigs indicate that protein kinase C might be involved in the mechanism of reduced Ca²⁺ responsiveness of myofilaments in stunned myocardium. However, at this stage no differences could be found between the maximal activity of the Ca²⁺-stimulated Mg²⁺-ATPase, the pCa₅₀ and the degree of phosphorylation of myofibrils isolated from stunned and non-stunned myocardium.     

The N-Terminal Extension of Cardiac Troponin T Stabilizes the Blocked State of Cardiac Thin Filament

Cardiac troponin T (cTnT) is a key component of contractile regulatory proteins. cTnT is characterized by a ～32 amino acid N-terminal extension (NTE), the function of which remains unknown. To understand its function, we generated a transgenic (TG) mouse line that expressed a recombinant chimeric cTnT in which the NTE of mouse cTnT was removed by replacing its 1–73 residues with the corresponding 1–41 residues of mouse fast skeletal TnT. Detergent-skinned papillary muscle fibers from non-TG (NTG) and TG mouse hearts were used to measure tension, ATPase activity, Ca²⁺ sensitivity (pCa₅₀) of tension, rate of tension redevelopment, dynamic muscle fiber stiffness, and maximal fiber shortening velocity at sarcomere lengths (SLs) of 1.9 and 2.3 μm. Ca²⁺ sensitivity increased significantly in TG fibers at both short SL (pCa₅₀ of 5.96 vs. 5.62 in NTG fibers) and long SL (pCa₅₀ of 6.10 vs. 5.76 in NTG fibers). Maximal cross-bridge turnover and detachment kinetics were unaltered in TG fibers. Our data suggest that the NTE constrains cardiac thin filament activation such that the transition of the thin filament from the blocked to the closed state becomes less responsive to Ca²⁺. Our finding has implications regarding the effect of tissue- and disease-related changes in cTnT isoforms on cardiac muscle function.     

Interactions of Lactobacillus bulgaricus Temperate Bacteriophage 0448 with Host Strains

Lactobacillus bulgaricus LT4(0448) is a lysogenic strain from which a temperate bacteriophage can be induced by mitomycin C or UV irradiation. Lactobacillus lactis CNRZ 326 is an indicator strain for the temperate phage 0448, but this strain lyses only in the presence of Ca²⁺ ions. A resistant culture developed secondarily after phage lysis and grew normally in MRS broth but again lysed abruptly if Ca²⁺ ions were added after two or three transfers. This behavior of the secondary culture and its subcultures is explained by a heterogeneous and fluctuating bacterial population, including clones identical to L. lactis 326, which were sensitive to 0448 and which formed rough colonies, as does the indicator. The proportion of these clones increased in the course of transfers in MRS, explaining lysis when Ca²⁺ was added. The population also included clones which formed smooth colonies (S clones). SI clones, which could not be induced by mitomycin C, were the major type in the initial culture, although they were sensitive to temperate phage 0448. The SI population then decreased and was gradually replaced by SII clones, inducible by mitomycin C and resistant to 0448. These SII clones were lysogenized clones, 326(0448), whose stability was confirmed by growth in the presence of an antiphage serum. When L. bulgaricus LT4(0448) was treated with mitomycin C, several cured LT4 clones were obtained that were related to the clones of the indicator L. lactis 326; they formed rough colonies. They also became sensitive to lytic phages or temperate phages active against L. lactis 326 and insensitive to lytic phages which lysed L. bulgaricus LT4(0448). This suggests that phage 0448 can lead to a lysogenic conversion of host strain LT4.     

Synchronous In Situ ATPase Activity, Mechanics, and Ca Sensitivity of Human and Porcine Myocardium

Flash-frozen myocardium samples provide a valuable means of correlating clinical cardiomyopathies with abnormalities in sarcomeric contractile and biochemical parameters. We examined flash-frozen left-ventricle human cardiomyocyte bundles from healthy donors to determine control parameters for isometric tension (P_o) development and Ca²⁺ sensitivity, while simultaneously measuring actomyosin ATPase activity in situ by a fluorimetric technique. P_o was 17 kN m⁻² and pCa_50% was 5.99 (28°C, I = 130 mM). ATPase activity increased linearly with tension to 132 μM s⁻¹. To determine the influence of flash-freezing, we compared the same parameters in both glycerinated and flash-frozen porcine left-ventricle trabeculae. P_o in glycerinated porcine myocardium was 25 kN m⁻², and maximum ATPase activity was 183 μM s⁻¹. In flash-frozen porcine myocardium, P_o was 16 kN m⁻² and maximum ATPase activity was 207 μM s⁻¹. pCa_50% was 5.77 in the glycerinated and 5.83 in the flash-frozen sample. Both passive and active stiffness of flash-frozen porcine myocardium were lower than for glycerinated tissue and similar to the human samples. Although lower stiffness and isometric tension development may indicate flash-freezing impairment of axial force transmission, we cannot exclude variability between samples as the cause. ATPase activity and pCa_50% were unaffected by flash-freezing. The lower ATPase activity measured in human tissue suggests a slower actomyosin turnover by the contractile proteins.     

The Effects of Ca2+ and MgADP on Force Development during and after Muscle Length Changes

The goal of this study was to compare the effects of Ca²⁺ and MgADP activation on force development in skeletal muscles during and after imposed length changes. Single fibres dissected from the rabbit psoas were (i) activated in pCa²⁺4.5 and pCa²⁺6.0, or (ii) activated in pCa²⁺4.5 before and after administration of 10 mM MgADP. Fibres were activated in sarcomere lengths (SL) of 2.65 µm and 2.95 µm, and subsequently stretched or shortened (5%SL at 1.0 SL.s⁻¹) to reach a final SL of 2.80 µm. The kinetics of force during stretch were not altered by pCa²⁺ or MgADP, but the fast change in the slope of force development (P₁) observed during shortening and the corresponding SL extension required to reach the change (L₁) were higher in pCa²⁺6.0 (P₁ = 0.22±0.02 P_o; L₁ = 5.26±0.24 nm.HS^.1) than in pCa²⁺4.5 (P₁ = 0.15±0.01 P_o; L₁ = 4.48±0.25 nm.HS^.1). L₁ was also increased by MgADP activation during shortening. Force enhancement after stretch was lower in pCa²⁺4.5 (14.9±5.4%) than in pCa²⁺6.0 (38.8±7.5%), while force depression after shortening was similar in both Ca²⁺ concentrations. The stiffness accompanied the force behavior after length changes in all situations. MgADP did not affect the force behavior after length changes, and stiffness did not accompany the changes in force development after stretch. Altogether, these results suggest that the mechanisms of force generation during and after stretch are different from those obtained during and after shortening.     

Effects of calcitonin and parathyroid hormone on the metabolism of chondrocytes in culture

Rabbit articular chondrocytes in suspension culture synthesize Type II colagen [3α₁(II)] in the absence of extracellular Ca²⁺ and Type Icollagen [2α₁?(I)·α₂] in the complete medium. As a result of pre-treatment in monolayer culture with calcitonin or parathyroid hormone in the complete medium, an influx of Ca²⁺ into the cells occurs. These cells produce mainly Type I collagen when transferred to suspension cultures in the medium devoid of CaCl₂. If added directly to the suspension culture medium containing no CaCl₂, calcitonin stimulates an active efflux of Ca²⁺ from the cells into the medium and leads the cells to synthesize Type I collagen. Under similar conditions, parathyroid hormone does not change the collagen-phenotype.     

Factors affecting biohydrogen production by unicellular halotolerant cyanobacterium Aphanothece halophytica

The effects of several physiological parameters on H₂ production rate in the unicellular halotolerant cyanobacterium Aphanothece halophytica were investigated. Under nitrogen deprivation, the growth of cells was inhibited, but H₂ production rate was enhanced approximately fourfold. Interestingly, cells grown under sulfur deprivation exhibited a decrease in cell growth, H₂ production rate, and bidirectional hydrogenase activity. Glucose was the preferred sugar source for H₂ production by A. halophytica, but H₂ production decreased at high glucose concentrations. H₂ production rate was optimum when cells were grown in the presence of 0.75 M?NaCl, or 0.4 μM?Fe³⁺, or 1 μM?Ni²⁺. The optimum light intensity and temperature for H₂ production were 30 μmol photons m^?2?s^?1 and 35 °C, respectively. A two-stage culture of A. halophytica was performed in order to overcome the reduction of cell growth in N-free medium. In the first stage, cells were grown in normal medium to accumulate biomass, and in the second stage, H₂ production by the obtained biomass was induced by growing cells in N-free medium supplemented with various chemicals for 24 h. A. halophytica grown in N-free medium containing various MgSO₄ concentrations had a high H₂ production rate between 11.432 and 12.767 μmol H₂ mg?chlorophyll a (chl a)^?1?h^?1, a 30-fold increase compared to cells grown in normal medium. The highest rate of 13.804 μmol H₂ mg?chl a ^?1?h^?1 was obtained when the N-free growth medium contained 0.4 μM Fe³⁺. These results suggested the possibility of using A. halophytica and some other halotolerant cyanobacteria thriving under extreme environmental conditions in the sea as potential sources for H₂ production in the future.     

Bacteriolytic activity of seminalplasmin

Seminalplasmin, an antimicrobial protein from bovine seminal plasma, lysed both Gram-positive and Gram-negative bacteria but not Candida albicans. The lytic activity was not lysozyme-like and was not affected by inhibitors of RNA or protein synthesis or by azide; it was strongly inhibited by divalent cations like Ca2+, Mn2+ and Mg2+ at millimolar concentrations. Maximum lysis of Escherichia coli was obtained at 37 degrees C; heat treatment of E. coli drastically reduced its susceptibility to lysis by seminalplasmin. E. coli cells in the stationary phase of growth were lysed much less than those in the exponential phase, and those grown in an enriched medium were lysed much more than those grown in a minimal medium. It appears that the lytic activity of seminalplasmin is due to the activation of an autolysin.     

Cytolytic T lymphocytes: an overview of their characteristics

Cloned T cells have been useful for assessing the lytic potential of distinct T cell subsets and for determining the relative contribution of different effector mechanism involved in the lytic process. Alloreactive CD8⁺ murine T cell clones and cloned murine CD4⁺ T_H1 and T_H2 T cells reactive with nominal antigen (ovalbumin) lysed nucleated target cells bearing antigen or coated with anti-CD3 monoclonal antibody in a short term⁵¹Cr-release assay. These clones were also evaluated for their ability to lyse efficiently sheep erythrocyte (SRBC) target cells coated with anti-CD3 mAb by a mechanism (presumably involving membrane damage) that does not involve nuclear degradation. Three patterns of lysis were observed: CD8⁺ and some CD4⁺ T_H2 effector cells lysed efficiently nucleated target cells and anucleated SRBC coated with anti-CD3 mAb. However, CD4⁺ T_H1 (and a few T_H2) T cells which lysed nucleated target cells bearing antigen or coated with anti-CD3 mAb didnotlyse efficiently the SRBC coated with anti-CD3 mAb. One CD4 bearing T_H2 cell failed to lyse efficiently either nucleated target cells or anucleated SRBC coated with anti-CD3 mAb. These results indicate that both T_H1 and T_H2 clones have lytic capabilities. Furthermore, they suggest that some but not all T_H2 murine T cell clones have lytic characteristics similar to those of conventional CD8⁺ CTL. However, it is not certain how these patterns of lysis of target cellsin vitro relates to the capacity of CTL to lyse such target cellsin vivo.     

Manganese dependent production of 5′-nucleotidase by alkalophilic Bacillus No. C-3

Alkalophilic Bacillus no. C-3 isolated from soil produced 5′-nucleotidase (EC 3.1.3.5) extracellularly when cultured in a medium containing Mn²⁺. The unique point of enzyme production is that the enzyme was produced well in the medium containing a rather high concentration of Mn²⁺, in spite of a small difference in growth. The optimum concentration of Mn²⁺ for the enzyme production was 10 mM and over. Mn²⁺ could not be replaced by other divalent cations when added singly. In the presence of 10 mM Mn²⁺, the enzyme production was repressed by the addition of 0.5 mM phosphate to the medium. The course of the enzyme production closely paralleled the increase in growth. The optimum pH for the enzyme activity was 9.2–9.5, and KHCO₃-K₂CO₃ buffer was suitable for the enzyme.     

Some characteristics of cotton pyrophosphatase activation by magnesium

The effect of Mg²⁺ ions on inducing pyrophosphatase activity of germinating cotton (Gossypium hirsutum L.) seeds was investigated. The presence of Mg²⁺ ions in the germination medium markedly shortened time for the attainment of the pyrophosphatase maximum activity (T _max). In the absence of Mg²⁺ ions in the nutrient medium, T _max comprised 6.0–6.5 days, whereas in the presence of 3–5 mM Mg²⁺, T _max was decreased to 3–4 days. An increase in the concentration of Mg²⁺ ions in the medium up to 5 mM resulted in an increase in pyrophosphatase activity. The effect of Mg²⁺ ions on the activity of a purified pyrophosphatase preparation isolated from three-day-old cotton seedlings was investigated. Mg²⁺ ions did not affect the rate of attainment of a maximum pyrophosphatase activity, but decreased the value of the Michaelis-Menten constant.     

17β-hydroxysteroid dehydrogenase activity in cultured myometrial cells: Effect of serial subcultures

17β-Hydroxysteroid dehydrogenase (17β-SDH) activity was studied in culture ovine rayometrial cells. After primary culture, cells were routinely subcultured (every 7th day), seeded at 5–10⁵ cells per dish and grown in a medium with 2% of serum. 17β-SDH activity was measured by incubating intact cell monolayers with [³H]-estradiol (5·10⁻⁶) in serum-free medium. Metabolites were extracted from both cells and medium, and separated by thin-layer chromatography. 17β-SDH was expressed as total E i formed (cells + medium) in fmol/mg of protein as a function of time. 17β-SDH has an approximate K_m of 5–10⁻⁶ M. After 3 min of incubation, all measurable E₁ is within the cells; it is progressively released but after l h only 40% of E₁ is found in the medium. 17β-SDH decreases from day 2 to day 8 of each subculture, whereas total proteins increase. Subculture partially restores 17β-SDH activity so that it is always higher on day 2 of any subculture than on day 8 of the previous one. however a progressive decline occurs with successive subcultures. This decline parallels the slowing of cell growth and overall protein synthesis and probably reflects cell ageing.     

Biological Control of Damping-Off of Alfalfa Seedlings with Bacillus cereus UW85

We explored the potential of biological control of alfalfa (Medicago sativa L.) seedling damping-off caused by Phytophthora megasperma f. sp. medicaginis by screening root-associated bacteria for disease suppression activity in a laboratory bioassay. A total of 700 bacterial strains were isolated from the roots of field-grown alfalfa plants by using Trypticase soy agar. A simple, rapid assay was developed to screen the bacteria for the ability to reduce the mortality of Iroquois alfalfa seedlings that were inoculated with P. megasperma f. sp. medicaginis zoospores. Two-day-old seedlings were planted in culture tubes containing moist vermiculite, and each tube was inoculated with a different bacterial culture. Sufficient P. megasperma f. sp. medicaginis zoospores were added to each tube to result in 100% mortality of control seedlings. Of the 700 bacterial isolates tested, only 1, which was identified as Bacillus cereus and designated UW85, reduced seedling mortality to 0% in the initial screen and in two secondary screens. Both fully sporulated cultures containing predominantly released spores and sterile filtrates of these cultures of UW85 were effective in protecting seedlings from damping-off; filtrates of cultures containing predominantly vegetative cells or endospores inside the parent cell had low biocontrol activity. Cultures grown in two semidefined media had significantly greater biocontrol activities than cultures grown in the complex tryptic soy medium. In a small-scale trial in a field infested with P. megasperma f. sp. medicaginis, coating seeds with UW85 significantly increased the emergence of alfalfa. The results suggest that UW85 may have potential as a biocontrol agent for alfalfa damping-off, thus providing an alternative to current disease control strategies.     

Lytic Action of Inducible Bacteriocin Clostocin O

Clostocin O had a remarkable lytic action toward the exponentially growing organisms of Clostridium saccharoperbutylacetonicum No. 8. The cellular lysis was inhibited by addition of heavy metal cations such as Cu²⁺, Ni²⁺, and Cd²⁺, or fradiomycin and RNase, which had been reported to be the inhibitors for lytic enzymes such as some of clostridial phage-endolysin and clostocin O-endolysin. The formalin-treated organisms and antibiotic-treated organisms, of which autolysin activity was inhibited, were also lysed by clostocin O. The induced cellular lysis by clostocin O was thought to be due to the lytic enzyme attached to clostocin O.     

THE ACCELERATING EFFECT OF MANGANOUS IONS ON PHAGE ACTION

Dilute solutions of MnCl₂ or MnSO₄ accelerate the lytic effect of phage upon susceptible staphylococci. Under the conditions of our experiments the manganese-containing mixtures lysed regularly 0.5 hour sooner than the controls. The effect is shown to be due to a lowering of the lytic threshold, i.e. the quantity of phage/bacterium requisite for lysis; Mn⁺⁺ reduces the ratio from 54 to about 12. In the presence of Mn⁺⁺ phage distribution is altered and in growing phage-bacteria mixtures the extracellular phage concentration is increased by manganese to approximately 4 times that occurring in the absence of manganese. There appears to be no enhancement of phage formation nor any affect on the rate of bacterial growth. As would be anticipated, for any given initial phage concentration the end titre after completion of lysis is less in the presence of manganese than in its absence. This is due to the reduced lytic threshold produced by Mn⁺⁺, there consequently being less phage needed to bring about lytic destruction of the bacteria.     

Behavior of Pythium torulosum Zoospores During Their Interaction with Tobacco Roots and Bacillus cereus

Bacillus cereus UW85 suppresses seedling damping-off diseases caused by Oomycetes and produces antibiotics that inhibit development of Oomycetes in culture. The goal of this study was to determine how UW85 and its antibiotics affected the behavior of an Oomycete, Pythium torulosum, in its interaction with plant roots. We studied tobacco seedlings inoculated with zoospores of P. torulosum and UW85 culture, culture filtrate, washed cells, antibiotics (zwittermicin A or kanosamine), purified from cultures of UW85, and UW030, a mutant of UW85 that does not suppress disease and does not produce the antibiotics. Microscopic observation revealed that all of the treatments inhibited zoospore activity around roots and encystment on roots. Treatment with UW85 culture, culture filtrate, zwittermicin A, or kanosamine delayed cyst germination and the elongation rate of germ tubes, whereas treatment with UW030 or washed UW85 cells did not. In an in vitro seedling bioassay of disease suppression, the antibiotics, zwittermicin A and kanosamine, suppressed disease singly or together, although UW85 culture suppressed disease more effectively than did the antibiotics. The results show that B. cereus cultures affect zoospore behavior in the presence of roots, and B. cereus-produced antibiotics, zwittermicin A and kanosamine, contribute to disease suppression and inhibition of germ tube elongation in the presence of the plant root. Received: 9 September 1998 / Accepted: 13 October 1998     

Anaerobic Degradation of Uric Acid by Gut Bacteria of Termites

A study was done of anaerobic degradation of uric acid (UA) by representative strains of uricolytic bacteria isolated from guts of Reticulitermes flavipes termites. Streptococcus strain UAD-1 degraded UA incompletely, secreting a fluorescent compound into the medium, unless formate (or a formicogenic compound) was present as a cosubstrate. Formate functioned as a reductant, and its oxidation to CO₂ by formate dehydrogenase provided 2H⁺ + 2e⁻ needed to drive uricolysis to completion. Uricolysis by Streptococcus UAD-1 thus corresponded to the following equation: 1UA + 1formate → 4CO₂ + 1acetate + 4NH₃. Urea did not appear to be an intermediate in CO₂ and NH₃ formation during uricolysis by strain UAD-1. Formate dehydrogenase and uricolytic activities of strain UAD-1 were inducible by growth of cells on UA. Bacteroides termitidis strain UAD-50 degraded UA as follows: 1UA → 3.5 CO₂ + 0.75acetate + 4NH₃. Exogenous formate was neither required for nor stimulatory to uricolysis by strain UAD-50. Studies of UA catabolism by Citrobacter strains were limited, because only small amounts of UA were metabolized by cells in liquid medium. Uricolytic activity of such bacteria in situ could be important to the carbon, nitrogen, and energy economy of R. flavipes.