Growth In Nutrient Broth Research Articles

The Indiscriminate Chemical Makeup of Secondary Metabolites Derived from Endophytes Harvested from Aloe barbadensis Miller in South Africa's Limpopo Region.

The efficacy of 23 bacterial isolates obtained from surface-sterilized stems and leaves of three medicinal plants (Aloe barbadensis Miller, Artemisia afra, and Moringa oleifera) was investigated in an endeavour to prevent the growth of Mycobacterium bovis using the cross-streak method. Endophytes were isolated by incubating sterile plant materials on nutrient agar at 30 °C for 5 days. Two isolates showing activity were subsequently utilized to produce the extracts. Whole-genome sequencing (WGC) was used to identify the isolates. Secondary metabolites produced after 7 days of growth in nutrient broth were harvested through extraction with ethyl acetate. The extracts were chemically profiled using gas chromatography-high resolution time-of-flight mass spectrometry (GC-HRTOF-MS). NCBI BLAST search results revealed that the isolated endophytes belonged to the Pseudomonas and Enterobacter genera, based on WGC. Two endophytes, Aloe I4 and Aloe I3-I5 from Aloe barbadensis, exhibited potency based on the cross-streak method. The metabolite profiling of the selected endophytes identified 34 metabolites from Aloe I4, including ergotamine, octadecane, L-proline and 143 other metabolites including quinoline and valeramide, which inhibit microbial quorum sensing. These findings suggest that bacterial endophytes from medicinal plants, particularly Aloe barbadensis, hold promise as sources of antimycobacterial agents for human health applications.

Isolation, identification, degradation mechanism and exploration of active enzymes in the ochratoxin A degrading strain Acinetobacter pittii AP19

Ochratoxin A (OTA) is a polyketide mycotoxin that commonly contaminates agricultural products and causes significant economic losses. In this study, the efficient OTA-degrading strain AP19 was isolated from vineyard soil and was identified as Acinetobacter pittii. Compared with growth in nutrient broth supplemented with OTA (OTA-NB), strain AP19 grew faster in nutrient broth (NB), but the ability of the resulting cell lysates to remove OTA was weaker. After cultivation in NB, the cell lysate of strain AP19 was able to remove 100% of 1 mg/L OTA within 18 h. The cell lysate fraction > 30 kDa degraded 100% of OTA within 12 h, while the fractions < 30 kDa were practically unable to degrade OTA. Further anion exchange chromatography of the > 30 kDa fraction yielded two peaks exhibiting significant OTA degradation activity. The degradation product was identified as OTα. Amino acid metabolism exhibited major transcriptional trends in the response of AP19 to OTA. The dacC gene encoding carboxypeptidase was identified as one of the contributors to OTA degradation. Soil samples inoculated with strain AP19 showed significant OTA degradation. These results provide significant insights into the discovery of novel functions in A. pittii, as well as its potential as an OTA decomposer.

Bacteriophage-mediated biosynthesis of MnO2NPs and MgONPs and their role in the protection of plants from bacterial pathogens.

Xanthomonas oryzae pv. oryzae (Xoo) is the plant pathogen of Bacterial Leaf Blight (BLB), which causes yield loss in rice. In this study, the lysate of Xoo bacteriophage X3 was used to mediate the bio-synthesis of MgO and MnO2. The physiochemical features of MgONPs and MnO2NPs were observed via Ultraviolet - Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Transmission/Scanning electron microscopy (TEM/SEM), Energy dispersive spectrum (EDS), and Fourier-transform infrared spectrum (FTIR). The impact of nanoparticles on plant growth and bacterial leaf blight disease were evaluated. Chlorophyll fluorescence was used to determine whether the nanoparticles application were toxic to the plants. An absorption peak of 215 and 230 nm for MgO and MnO2, respectively, confirmed nanoparticle formation via UV-Vis. The crystalline nature of the nanoparticles was detected by the analysis of XRD. Bacteriological tests indicated that MgONPs and MnO2NPs sized 12.5 and 9.8 nm, respectively, had strong in vitro antibacterial effects on rice bacterial blight pathogen, Xoo. MnO2NPs were found to have the most significant antagonist effect on nutrient agar plates, while MgONPs had the most significant impact on bacterial growth in nutrient broth and on cellular efflux. Furthermore, no toxicity to plants was observed for MgONPs and MnO2NPs, indeed, MgONPs at 200 μg/mL significantly increased the quantum efficiency of PSII photochemistry on the model plant, Arabidopsis, in light (ΦPSII) compared to other interactions. Additionally, significant suppression of BLB was noted in rice seedlings amended with the synthesized MgONPs and MnO2NPs. MnO2NPs showed promotion of plant growth in the presence of Xoo compared to MgONPs. An effective alternative for the biological production of MgONPs and MnO2NPs was reported, which serves as an effective substitute to control plant bacterial disease with no phytotoxic effect.

Bacterium isolated from coffee waste pulp biosorps lead: Investigation of EPS mediated mechanism.

Kleibsiella pneumoniae Kpn555, isolated from coffee waste pulp showed high level of tolerance to lead with a minimum inhibitory concentration of 900mg/L. On its growth in nutrient broth supplemented with lead, brown clumps were visualised at the bottom of the flask. On scanning and transmission electron microscopic studies the brown clumps were corroborated to be bacterial cells with lead biosorbed on the cell surface and accumulated inside the cytoplasm. Biochemical and FT-IR analysis of the extracellular polymeric substance produced on exposure to lead revealed its chemical nature as glycolipid with protein moieties. Purified EPS (100mg/L) could remove 50% of lead from aqueous solution (200mg/L). Isolation of plasmid from Klebsiella pneumoniae Kpn555 revealed the presence of a plasmid of size 30-40kb. This capability of the bacteria was proven to be plasmid mediated as the Escherichia coli DH5α cells transformed with the plasmid of Klebsiella pneumoniae Kpn555 also could tolerate 900mg/L of lead and form brown clumps. This study shows that these bacteria, aided by EPS could serve as an effective agent for the removal of lead from contaminated water environmental samples.

Extracellular Synthesis and Characterization of Silver Nanoparticles from Alkaliphilic Pseudomonas sp.

Bio-nanotechnology offers eco-friendly processes for the synthesis of stable nanoparticles (NPs). We hypothesized that microorganisms isolated from the root nodules of leguminous plants would biosynthesize silver (Ag) bio-nanoparticles. Clover root nodules enriched with nutrient broth (NB) produced four distinct colonies on NA plates. Microbial colonies were purified by repeated streaking and designated as SS6, SS7, SS8, and SS9 for identification using 16S rRNA sequencing. Four species of Pseudomonas were identified with a similarity score of over 99% using the EZ Taxon search engine, and tested for extracellular biosynthesis of AgNPs. Microorganism Pseudomonas taiwanensis-SS8 with alkaliphilic growth characteristics reduced the AgNO3 solution into AgNPs in the shortest time period. AgNPs were characterized using UV-Vis spectrophotometry and electron and transmission electron microscopy. A number of physical (i.e., temperature and time) and chemical (i.e., pH and growth media) parameters were optimized. An efficient polydispersal biosynthesis of AgNPs at pH 8-9 after 48 hrs in NB growth medium was observed. In addition, the AgNPs showed antimicrobial properties against 16 commonly occurring pathogenic microorganisms.

Comparison of Thioglycollate Broth with Liver Extract (BQ Vaccine Medium) with Traditionally Used Culture Media for Mass Scale Production of Clostridium perfringens Type D

Thioglycollate broth with Liver Extract (BQ vaccine medium) was used to produce mass scale yield of Clostridium perfringens Type D. Upon growth of Clostridium perfringens in different culture media the OD value of bacterial growth in BQ vaccine medium, Reinforced Culture Medium (RCM), Cooked Meat Medium (CMM) and Nutrient Broth (NB) was 2.260, 2.184, 2.096 and 1.984 respectively. Mice Lethality result of growth in BQ vaccine medium was equal to that of RCM while growth in CMM and NB had very less lethality. ELISA percentage positivity for Epsilon toxins in the supernatant of growth in BQ medium at 450 nm wavelength at dilution of 320 and 640 was higher than that of all the culture media under comparison. It was concluded that BQ was an excellent culture medium for the development of Enterotoxaemia vaccine producing maximum concentration of epsilon toxin than any culture media used before.

The Survival of Endophytic Bacteria Isolated from Jerusalem Artichoke In Drought Conditions

Four endophytic bacteria isolated from Jerusalem artichoke had the ability of plant growth promotion. These bacteria, isolate 3.13, 4.43, 5.2 and 5.18, were selected to study the promotion of plant growth in drought condition. Thus, survival of the bacteria under drought condition needed for the investigation. All four isolates showed the growth in Nutrient Broth (NB) containing 20% Polyethylene Glycol (PEG). Moreover, all four isolates were tested their survival in NB with 20% PEG and soil by incubating at 30, 35, 40 and 45â—¦C. Reasonable survival was observed in all isolates at 30 to 40â—¦C of both media. Furthermore, isolate 5.18 demonstrated the growth at 45â—¦C and maintained cell numbers at 4.19A—104 CFU/mL after 29 days and 1.30A—107 CFU/mL after 57 days in NB with 20% PEG and in the soil, respectively.

Carvacrol nanoemulsion combined with acid electrolysed water to inactivate bacteria, yeast in vitro and native microflora on shredded cabbages

Carvacrol is an effective antimicrobial agent originated from essential oils, this natural antimicrobial agent has higher consumer acceptance compared to chemical agents. Due to the low solubility of carvacrol in water, carvacrol was delivered as a nanoemulsion. A carvacrol nanoemulsion contained 3.5% (w/w) oil phase (1% carvacrol and 2.5% corn oil, w/w) and 3.5% (w/w) Tween 80 was produced by ultrasonification at 10 min using 100% amplitude; the median particle size was 309 ± 19 nm. The nanoemulsion was shelf-life stable for 1 month without any significant changes in particle size. When applied against Escherichia coli ATCC 25922 and Pichia pastoris GS115 growth in nutrient broth, carvacrol nanoemulsion (0.5% w/w carvacrol) achieved 3 log reductions of microorganisms. When microorganisms were fixed and dried on stainless steel coupon surface, the carvacrol nanoemulsion treatment was more effective on E. coli than P. pastoris with about 5 and 0.3 log reduction of viable count, respectively. The native microflora on shredded cabbages was challenged by combining carvacrol nanoemulsion and acidic electrolysed water (AEW) that contained ≤ 4 mg/L free available chlorine (FAC). The treatment reduced about 0.5 log of aerobic mesophilic and psychrotropic bacteria counts and the antimicrobial activity of carvacrol nanoemulsion and AEW lasted up to 2 days. The results indicated that carvacrol nanoemulsion is promising in controlling the safety of fresh-cut vegetables.

A novel alkaline serine protease from bacillus amyloliquefaciens strain S1-13

Bacillus sp. strain S1-13 was identified as Bacillus amyloliquefaciens with 16s rRNA gene (Accession number: JX441363). The strain S1-13 was expressed and secreted alkaline serine protease (called ASP1-13) when growth in nutrient broth containing with 1% skim milk. ASP1-13 was partial purified with a specific activity of 1,324 U/mg and 2% yield. The molecular weight and isoelectric point of ASP1-13 was determined about 40 kDa and 8, respectively. It was indicated as alkaline serine protease with a broad range of activity at alkaline condition (pH 7-12) and completely inhibited with serine protease inhibitor. ASP1-13 was also active in high temperature (50-60°C) and stabilizes with broad range of pH (5-12), surfactant, oxidant, reducing agent and organic solvent. Finally, the partial amino acid sequence from LC/MS-MS was confirmed similarity with sequence of neutral protease precursor from Bacillus subtilis.

Degradation kinetics and pathway of phenol by Pseudomonas and Bacillus species

This article elucidates that strain Pseudomonas aeruginosa (IES-Ps-1) is a versatile toxic organic compound degrader. With the degradation of malathion and cypermethrin (studied by other researchers previously), this strain was able to degrade phenol. Two other indigenous soil flora (i.e., Pseudomonas sp. (IES-S) and Bacillus subtilis (IES-B)) were also found to be potential phenol degraders.Phenol was degraded with Monod kinetics during growth in nutrient broth and mineral salts medium. Before entering into the growth inhibition phase, strains IES-Ps-1, IES-S and IES-B could tolerate up to 400, 700 and 500 mg/L phenol, respectively, when contained in nutrient broth. However, according to the Luong–Levenspiel model, the growth of strains IES-Ps-1, IES-S and IES-B would cease at 2000, 2174 and 2190 mg/L phenol, respectively. Strain IES-Ps-1 degraded 700, 900 and 1050 mg/L phenol contained in mineral salts medium with the specific rates of 0.034, 0.075 and 0.021 h−1, respectively. All these strains grew by making clusters when exposed to phenol in order to prevent damages due to high substrate concentration. These strains transformed phenol into catechol, which was then degraded via ortho-cleavage pathway.

To be or not to be a poly(3-hydroxybutyrate) (PHB) depolymerase: PhaZd1 (PhaZ6) and PhaZd2 (PhaZ7) of Ralstonia eutropha, highly active PHB depolymerases with no detectable role in mobilization of accumulated PHB.

The putative physiological functions of two related intracellular poly(3-hydroxybutyrate) (PHB) depolymerases, PhaZd1 and PhaZd2, of Ralstonia eutropha H16 were investigated. Purified PhaZd1 and PhaZd2 were active with native PHB granules in vitro. Partial removal of the proteinaceous surface layer of native PHB granules by trypsin treatment or the use of PHB granules isolated from ΔphaP1 or ΔphaP1-phaP5 mutant strains resulted in increased specific PHB depolymerase activity, especially for PhaZd2. Constitutive expression of PhaZd1 or PhaZd2 reduced or even prevented the accumulation of PHB under PHB-permissive conditions in vivo. Expression of translational fusions of enhanced yellow fluorescent protein (EYFP) with PhaZd1 and PhaZd2 in which the active-site serines (S190 and Ser193) were replaced with alanine resulted in the colocalization of only PhaZd1 fusions with PHB granules. C-terminal fusions of inactive PhaZd2(S193A) with EYFP revealed the presence of spindle-like structures, and no colocalization with PHB granules was observed. Chromosomal deletion of phaZd1, phaZd2, or both depolymerase genes had no significant effect on PHB accumulation and mobilization during growth in nutrient broth (NB) or NB-gluconate medium. Moreover, neither proteome analysis of purified native PHB granules nor lacZ fusion studies gave any indication that PhaZd1 or PhaZd2 was detectably present in the PHB granule fraction or expressed at all during growth on NB-gluconate medium. In conclusion, PhaZd1 and PhaZd2 are two PHB depolymerases with a high capacity to degrade PHB when artificially expressed but are apparently not involved in PHB mobilization in the wild type. The true in vivo functions of PhaZd1 and PhaZd2 remain obscure.

Comparative antibacterial activity of different plant extracts in relation to their bioactive molecules, as determined by LC-MS analysis.

The research of plant responses against antibiotics and chemical disinfectants is increasingly motivated by natural antimicrobial agents. We investigated hydrophilic extracts of leaves of Persian walnut (Juglans regia ) and European Mistletoe (Viscum album) and White willow bark (Salix alba ) which were characterized by their content in phenolic derivatives, using a high-throughput technique, HPLC-DAD. The extracts were obtained using 10% dry plant and hot acidulated water (around 85 0 C) and kept for 48 hours then diluted successively (from 2 to 9 times). The antimicrobial activities were tested semi-quantitative ly on agar plates inoculated with E. Coli, Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus and Salmonella enteritis. The inhibition zones were measured after 24 hours of incubation. Using a liquid nutrient broth growth medium, a quantitative evaluation of antimicrobial effect was done. There were noticed to be significant the growth rates in the first 10 hours, the best inhibitory results being given by Salix alba extract which inhibited all bacteria. Meanwhile, walnut and mistletoe extracts showed different inhibition rates, depending on the bacteria and the extract dilution. The extracts’ composition as determined by HPLC was compared with the antimicrobial activity, suggesting that willow extract is the richest in phenolics, especially in phenolic acids (salicylic acid derivatives). This study suggest that Salix alba bark and Juglans regia are available and efficient sources of natural antimicrobials and suggests the possibility of using their hydrophilic extracts as bio-disinfectants in food industry.

Inhibition of growth and caseinase production ofPseudomonas aeruginosaandEscherichia coli28 by combination of low pH and NaCl, potassium sorbate orThymus vulgarisextract

Previous studies reported that, at neutral pH (e.g. 7.4), many preservatives do not have antimicrobial effect against Pseudomonas aeruginosa and some strains of E. coli . This study investigated the effect of combination of low pH and some preservatives (e.g. sodium chloride, potassium sorbate or Thymus vulgaris extract) on the growth and caseinase production of Pseudomonas aeruginosa and E. coli at 31 degrees C and 7 degrees C. At 31 degrees C, although growth of the strains was not affected by low pH (5.7) alone, caseinase production by both strains was decreased. A combination of low pH and NaCl, potassium sorbate or thyme extract significantly reduced (p < 0.05) growth and caseinase production by E. coli 28 at 31 degrees C. For P. aeruginosa , addition of NaCl or thyme extract to nutrient broth (low pH) did not affect the growth but reduced caseinase production of the tested strain. Combination of low temperature (7 degrees C) and growth in nutrient broth (low pH) plus sodium chloride or nutrient broth (low pH) plus potassium sorbate was the most effective treatment in reducing or inhibiting growth and caseinase production of the tested strains.

Expression of Staphylococcus epidermidis SdrG Increases following Exposure to an In Vivo Environment

SdrG is a surface-associated fibrinogen binding protein present in most strains of Staphylococcus epidermidis. Surface expression of SdrG was not detected by flow cytometry or immunofluorescence microscopy on S. epidermidis 0-47 grown in nutrient broth or in the presence of human serum. sdrG transcript levels increased 1 hour following a shift from growth in nutrient broth to growth in the bloodstream of a mouse and resulted in a concomitant increase in protein levels as detected by immunofluorescence microscopy. The environmental signal(s) resulting in the increase in expression is elusive, as growth under conditions known to mimic in vivo conditions (elevated CO(2), iron limitation, human serum, and citrated human blood) did not affect expression of SdrG. Immunizing mice with either the N1N2N3 (amino acids 50 to 597) or N2N3 (amino acids 273 to 597) subdomain of the N-terminal A domain of recombinant SdrG (rSdrG) elicited a robust antibody response; however, only mice vaccinated with rSdrG(N23) exhibited a significant reduction in 0-47 recovered after experimental infection. Since SdrG is expressed early during infection in response to specific host environmental cues present in the bloodstream and since antibodies to it are effective in reducing bacteremia, SdrG possesses attributes of a vaccine component effective against the pathogenic form of the ubiquitous human commensal S. epidermidis.

Elimination by ozone of Shigella sonnei in shredded lettuce and water

Several outbreaks of shigellosis have been attributed to the consumption of contaminated fresh-cut vegetables. The minimal processing of these products make it difficult to ensure that fresh produce is safe for consumer. Chlorine-based agents have been often used to sanitize produce and reduce microbial populations in water applied during processing operations. However, the limited efficacy of chlorine-based agents and the production of chlorinated organic compounds with potential carcinogenic action have created the need to investigate the effectiveness of new decontamination techniques. In this study, the ability of ozone to inactivate S. sonnei inoculated on shredded lettuce and in water was evaluated. Furthermore, several disinfection kinetic models were considered to predict S. sonnei inactivation with ozone. Treatments with ozone (1.6 and 2.2 ppm) for 1 min decreased S. sonnei population in water by 3.7 and 5.6 log cfu mL −1, respectively. Additionally, it was found that S. sonnei growth in nutrient broth was affected by ozone treatments. After 5.4 ppm s ozone dose, lag-phases were longer for injured cells recovered at 10 °C than 37 °C. Furthermore, treated cells recovered in nutrient broth at 10 °C were unable to grow after 16.5 ppm s ozone dose. Finally, after 5 min, S. sonnei counts were reduced by 0.9 and 1.4 log units in those shredded lettuce samples washed with 2 ppm of ozonated water with or without UV-C activation, respectively. In addition, S. sonnei counts were reduced by 1.8 log units in lettuce treated with 5 ppm for 5 min. Therefore, ozone can be an alternative treatment to chlorine for disinfection of wash water and for reduction of microbial population on fresh produce due to it decomposes to nontoxic products.

Effect of environmental parameters on growth kinetics of Bacillus cereus (ATCC 7004) after mild heat treatment

The influence of temperature (10 to 50 °C), initial pH (4.0 to 6.0) and sodium chloride concentration (0.5 to 3.0%) on the growth in nutrient broth and in meat extract of Bacillus cereus after mild heat treatment (90 °C—10 min) was determined. B. cereus spores survived after heating and they were able to germinate and grow in both media when post-treatment conditions were favourable. Heated B. cereus did not grow at 10 and 50 °C or in a medium with pH 4.0. Decreasing pH values and increasing levels of sodium chloride decreased growth rate and increased the lag phase of B. cereus. pH 4.5 was unable to prevent the growth of heated spores in a meat substrate with 0.5% NaCl at 12 °C. The combination of pH ≤ 4.5, NaCl concentration ≥ 1.0% and temperatures ≤ 12 °C was sufficient to inhibit B. cereus growth after heat treatment at 90 °C for 10 min, for at least 50 days in nutrient broth and in meat extract. Re-heating at temperatures ≥ 60 °C could control heated B. cereus ATCC 7004 growth.

Isolation of ice-nucleating active bacterium from mackerel and its properties

ABSTRACT: An ice-nucleating bacterium, designated MACK-4, was isolated from ice-stored mackerel (Scomber australasicus) and identified as a Pseudomonas fluorescens. The optimal temperature and pH for its growth in nutrient broth with 2.5% glycerol (NB-G) were 15°C and 6.5, respectively. The maximal ice-nucleating activity (INA) was obtained after 54 h incubation at 15°C. However, the INA was almost completely lost after 48 h incubation at 25°C or higher. The growth and INA decreased with increase of NaCl added in NB-G within 0.0–4.0%. The INA of MACK-4 was very stable at 5–25°C, pH 4.0–9.5, while that of isolated ice-nucleating matter from MACK-4 was stable at 5–25°C, pH 5.5–9.0.

Mutations that relieve nutritional repression of the Bacillus subtilis dipeptide permease operon

The Bacillus subtilis dciA operon encodes a dipeptide transport complex that is induced rapidly as cells enter stationary phase and initiate sporulation. Expression of this operon in growing cells is repressed by glucose, by a mixture of amino acids, and by the AbrB protein. A genetic screen was devised to identify mutations that allow inappropriate expression from the dciA promoter during growth. These mutations resulted in increased dciA transcription during growth in nutrient broth, in minimal amino acids medium, and in minimal glucose medium. Some of the mutations, called dcs (dciA control site), were cloned and shown by sequence analysis to cluster near the start site of dciA transcription. Primer extension and in vitro transcription analysis revealed that the dcs mutations did not create a new promoter. These mutations may therefore disrupt an operator site necessary for the binding of a negative regulator responsive to the nutritional state of the cell. The dcs mutant promoters were still subject to AbrB control, suggesting that the dciA operon is regulated by at least two proteins, AbrB and a nutritionally responsive regulator. The gene(s) for the putative nutritional regulator may be defined by the cod (control of dciA) mutations, which appeared to relieve amino acid and glucose repression of dciA by altering a diffusible factor. An abrB cod double mutant exhibited high-level expression of dciA during exponential growth phase.

A Pseudomonas strain accumulating polyesters of 3-hydroxybutyric acid and medium-chain-length 3-hydroxyalkanoic acids

A citronellol-utilizing bacterium was isolated that accumulated a polyester consisting of 3-hydroxybutyric acid (3HB) and of medium-chain-length 3-hydroxyalkanoic acids (3HAMCL) from various carbon sources up to approximately 70% of the cellular dry matter if the cells were cultivated in ammineral salts medium under nitrogen limitation. In octanoate-grown cells, for instance, the polyester consisted of 87.5 mol% 3HB and 12.5 mol% 3-hydroxyoctanoic acid (3HO), whereas it consisted of 10.3 mol% 3HB, 16.7 mol% 3HO and 73.0 mol% 3-hydroxydecanoic acid (3HD) in gluconate-grown cells. However, the results of various experiments indicated that a blend rather than a copolyester was synthesized in the cell. It was the only strain among 45 different recently isolated citronellol-utilizing bacteria that accumulated such a polyester. All other citronellol-utilizing bacteria behaved like Pseudomonas aeruginosa with respect to their polyhydroxyalkanoic acid (PHA) biosynthetic capabilities and accumulated PHA consisting of 3HAMCL with 3HO and 3HD as the main constituents from octanoate or gluconate, respectively, whereas 3HB was never present. None of 232 different heavy-metal-resistant bacteria was able to accumulate PHA composed of 3HB plus, for example, 3HO. Only 20.3% did not accumulate any PHA at all, 44.8% accumulated PHB from gluconate, and 34.9% behaved like P. aeruginosa. Many bacteria belonging to the latter group were distinguished from the other by rapid growth in nutrient broth and in gluconate mineral salts medium and by their ability to grow in the presence of a high concentration (up to 1.5%, w/v) of octanoate.

Nickel availability and urease expression in Proteus mirabilis

Cells of Proteus mirabilis, previously grown in nutrient broth (NB), exhibited an increase in urease activity during subsequent incubation in mineral medium even when protein biosynthesis was inhibited. During growth in NB, degradation of amino acids obviously led to the formation of nickel-complexing metabolites, and nickel ions were therefore unavailable for maximal expression of enzymatically active urease; this inhibition of urease biosynthesis was overcome by the addition of nickel to the growth medium, and also by added glucose. Experiments concerning the incorporation of radioactive nickel into urease finally indicated that the observed increase in urease activity was caused by posttranslational insertion of nickel into performed apo-urease.