SCL-LCL-PHA copolymer production by a local isolate,Pseudomonas aeruginosa MTCC 7925

A five-level-four-factor central composite rotary design (CCRD) was employed in combination with response surface methodology (RSM) to optimize the process variables for the production of a novel copolymer consisting of short-chain-length (SCL) and long-chain-length (LCL) PHA units, i.e., P(3HB-3HV-3HHD-3HOD) copolymer in Pseudomonas aeruginosa MTCC 7925. The four variables involved in this study were ethanol, glucose, ammonium nitrate (NH₄NO₃), and potassium dihydrogen phosphate (KH₂PO₄). A second-order polynomial equation was obtained by multiple regression analysis using RSM. The statistical analyses of the results showed that all the four variables had significant impact on the copolymer yield. The model predicted a maximum yield of 81.1% of dry cell weight (dcw) on setting the concentrations of ethanol and glucose at 1.5 and 1.1%, and KH₂PO₄ and NH₄NO₃ at 2.79 and 1.86 g/L, respectively. Verification of the predicted value resulted into a yield of 77.6% (dcw). This novel copolymer exhibited comparable material properties with polypropylene (PP) and low density polyethylene (LDPE), thus advocating its potential applications in various fields.     

Exploitation of inexpensive substrates for production of a novel SCL–LCL-PHA co-polymer by <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> MTCC 7925

Studies conducted with various inexpensive carbon sources such as whey, vegetable oils (palm, mustard, soybean and coconut), a low-cost source of glucose-D, rice and wheat bran, and mustard and palm oil cakes demonstrated palm oil as the best substrate for accumulation of a novel short-chain-length–long-chain-length polyhydroxyalkanoate (SCL–LCL-PHA) co-polymer containing SCL 3HAs [3-hydroxybutyric acid (3HB) and 3-hydroxyvaleric acid (3HV)] and LCL 3HAs of 3-hydroxyhexadecanoic acid (3HHD) and 3-hydroxyoctadecanoic acid (3HOD) units as constituents by a sludge-isolated Pseudomonas aeruginosa MTCC 7925. The co-polymer content reached up to 60% of dry cell weight (dcw) at 48 h of incubation in 0.5% (v/v) palm oil and the extract of 0.5% (v/v) palm oil cake supplemented vessels. The PHAs pool was further enhanced up to 69 and 75% (dcw), when the above culture was subjected to P- and N-limitation, respectively. The mol fraction of 3HB:3HV:3HHD:3HOD units were, respectively, 83.1:7.7:3.8:5.4 and 87.3:5.1:3.6:4.0 in P- and N-limited cultures. Consequently, a co-polymer yield of 5 g l⁻¹ (approx.) was achieved, which was about 80-fold higher as compared to 69 mg l⁻¹ of the control culture. On substrate basis, the accumulation reached up to 0.62 g PHAs per g substrate, which was significantly higher as compared to the yield obtained from starch by Haloferax mediterranei and Azotobacter chroococum, from molasses by A. vinelandii UWD, and from lactose and xylose by Pseudomonas cepacia. This novel P(3HB-co-3HV-co-3HHD-co-3HOD) co-polymer exhibited better thermal and mechanical properties as revealed from the differential scanning calorimetry and mechanical property studies, thus opens up new possibilities for various industrial applications.     

Reward for Bdellovibrio bacteriovorus for preying on a polyhydroxyalkanoate producer

Bdellovibrio bacteriovorus HD100 is an obligate predator that invades and grows within the periplasm of Gram‐negative bacteria, including mcl‐polyhydroxyalkanoate (PHA) producers such as Pseudomonas putida. We investigated the impact of prey PHA content on the predator fitness and the potential advantages for preying on a PHA producer. Using a new procedure to control P. putida KT2442 cell size we demonstrated that the number of Bdellovibrio progeny depends on the prey biomass and not on the viable prey cell number or PHA content. The presence of mcl‐PHA hydrolysed products in the culture supernatant after predation on P. putida KT42Z, a PHA producing strain lacking PhaZ depolymerase, confirmed the ability of Bdellovibrio to degrade the prey's PHA. Predator motility was higher when growing on PHA accumulating prey. External addition of PHA polymer (latex suspension) to Bdellovibrio preying on the PHA minus mutant P. putida KT42C1 restored predator movement, suggesting that PHA is a key prey component to sustain predator swimming speed. High velocities observed in Bdellovibrio preying on the PHA producing strain were correlated to high intracellular ATP levels of the predator. These effects brought Bdellovibrio fitness benefits as predation on PHA producers was more efficient than predation on non‐producing bacteria.     

Incorporation of polyethylene glycol in polyhydroxyalkanoic acids accumulated by Azotobacter chroococcum MAL-201

Azotobacter chroococcum MAL-201 (MTCC 3853), a free-living nitrogen-fixing bacterium accumulates poly(3-hydroxybutyric acid) [PHB, 69% of cell dry weight (CDW)] when grown on glucose and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [PHBV with 19.2 mol% 3HV] when grown on glucose and valerate. Use of ethylene glycol (EG) and/or polyethylene glycols (PEGs) of low molecular weight as sole carbon source were detrimental to A. chroococcum growth and polymer yields. PEG-200, however, in the presence of glucose was incorporated into the polyhydroxyalkanoate (PHA) polymer. Addition of PEG-200 (150 mM) to culture medium during mid-log phase growth favored increased incorporation of EG units (12.48 mol%) into the PHB polymer. In two-step culture experiments, where valerate and PEG simultaneously were used in fresh medium, EG was incorporated most effectively in the absence of glucose, leading to the formation of a copolymer containing 18.05 mol% 3HV and 14.78 mol% EG. The physico-mechanical properties of PEG-containing copolymer (PHBV–PEG) were compared with those of the PHB homopolymer and the PHBV copolymer. The PHBV–PEG copolymer appeared to have less crystallinity and greater flexibility than the short-chain-length (SCL) PHA polymers.     

PHAMCL biosynthesis systems in Pseudomonas aeruginosa and Pseudomonas putida strains show differences on monomer specificities

The production of PHA from plant oils by Pseudomonas species soil isolated from a sugarcane crop was evaluated. Out of 22 bacterial strains three were able to use efficiently plant oils to grow and to accumulate PHA. Pseudomonas putida and Pseudomonas aeruginosa strains produced PHA presenting differences on monomer composition compatible with variability on monomer specificity of their PHA biosynthesis system. The molar fraction of 3-hydroxydodecanoate detected in the PHA was linearly correlated to the oleic acid supplied. A non-linear relationship between the molar fractions of 3-hydroxy-6-dodecenoate (3HDdΔ₆) detected in PHA and the linoleic acid supplied was observed, compatible with saturation in the biosynthesis system capability to channel intermediate of β-oxidation to PHA synthesis. Although P. putida showed a higher 3HDdΔ₆ yield from linoleic acid when compared to P. aeruginosa, in both species it was less than 10% of the maximum theoretical value. These results contribute to the knowledge about the biosynthesis of PHA with a controlled composition from plant oils allowing in the future establishing the production of these polyesters as tailor-made polymers.     

Enantioselective transesterification of racemic phenyl ethanol and its derivatives in organic solvent and ionic liquid using Pseudomonas aeruginosa lipase

The transesterification of 1-phenyl ethanol has been carried out using lipases from Pseudomonas aeruginosa MTCC 5113, to obtain chirally pure aryl ethanols with good yield and excellent enantioselectivity. The lipase from P. aeruginosa gave good conversion and moderate enantioselectivity (ee) in organic solvents, however, when the catalytic amount of ionic liquids were added in the reaction mixture, excellent enantioselectivity was obtained. Moreover, the change in enantiomer preference was seen in the presence of catalytic amount of ionic liquids. The findings revealed that hydrophobic ionic liquids (two-phase system) were the best solvents and 4-substituted aryl ethanols were the pre-eminent substrates for such type of reactions. The preparative scale (5 g) transesterification of 1-phenylethanol using lipases from P. aeruginosa yielded S-(−)-1-phenyl ethanol with 39% yield and >99% ee in hexane and 46% yield and >99% ee in [BMIm][PF₆].     

Microbial Secretion Platform for 3‐Hydroxybutyrate Oligomer and Its End‐Capped Forms Using Chain Transfer Reaction‐Mediated Polyhydroxyalkanoate Synthases

The biodegradable polyester 3‐hydroxybutyrate (3HB) polymer [P(3HB)] is intracellularly synthesized and accumulated in recombinant Escherichia coli. In this study, native polyhydroxyalkanoate (PHA) synthases are used to attempt to microbially secrete 3HB homo‐oligomers (3HBOs), which are widely distributed in nature as physiologically active substances. High secretory production is observed, especially for the two PHA synthases from Aeromonas caviae and Bacillus cereus YB4. Surprisingly, an ethyl ester at the carboxy terminus (ethyl ester form) of 3HBOs is identified for most of the PHA synthases tested. Next, 3HBOs with a functional carboxyl group (carboxyl form of 3HBO) are obtained by using the alcohol dehydrogenase gene (adhE)‐deficient mutant strain, suggesting that the endogenous ethanol produced in E. coli acts as a chain transfer (CT) agent in the generation of 3HBOs. Furthermore, an in vitro polymerization assay reveals that CT agents such as ethanol and free 3HB are involved in the generation of ethyl ester and carboxyl form of 3HBO, respectively. The microbial platform established herein allows the secretion of 3HBOs with desirable end structures by supplementation with various CT agents. The obtained 3HBOs and their end‐capped forms may be used as physiologically active substances and building blocks for polymeric materials.     

Biosynthesis of novel polyhydroxyalkanoate containing 3-hydroxy-4-methylvalerate by Chromobacterium sp. USM2

Aims: Polyhydroxyalkanoate (PHA) with enhanced physicochemical properties will be ideal for a wide range of practical applications. The incorporation of 3‐hydroxy‐4‐methylvalerate (3H4MV) into the polymer backbone is known to improve the overall properties of the resulting polymer. However, the most suitable micro‐organism and PHA synthase that can synthesize this monomer efficiently still remain unknown at present. Therefore, we evaluated the abilities of a locally isolated Chromobacterium sp. USM2 to produce PHA containing 3H4MV. Methods and Results: The ability of Chromobacterium sp. USM2 to synthesize poly(3‐hydroxybutyrate‐co‐3‐hydroxy‐4‐methylvalerate) [P(3HB‐co‐3H4MV)] was evaluated under different culture conditions. It was found that Chromobacterium sp. USM2 can synthesize P(3HB‐co‐3H4MV) when glucose and isocaproic acid were fed as carbon source. However, the highest molar fraction of 3H4MV, 22 mol% was detected in Chromobacterium sp. USM2 when isocaproic acid was provided as the sole carbon source. In addition, aeration was identified as a crucial factor in initiating the accumulation of high 3H4MV molar fractions. Conclusions: Chromobacterium sp. USM2 was able to synthesize broad comonomer compositional distribution of P(3HB‐co‐3H4MV). Significance and Impact of the Study: Compared with Cupriavidus necator and Burkholderia sp., Chromobacterium sp. USM2 was found to have better ability to bioconvert isocaproic acid to form 3H4MV unit.     

Lactoferrin‐derived peptides and Lactoferricin chimera inhibit virulence factor production and biofilm formation in Pseudomonas aeruginosa

Aims: To investigate the bactericidal activity of lactoferrin‐derived peptides and a new LF‐derived peptides chimera (LFchimera) against P. aeruginosa and the influence on virulence factors of P. aeruginosa. Methods and Results: Lactoferricin (LFcin) and lactoferrampin (LFampin) are highly bioactive peptides isolated from the N‐terminal region of lactoferrin (LF) by pepsin digestion. In this study, we designed LFchimera containing LFcin amino acids 17‐30 and LFampin amino acids 268‐284. Pseudomonas aeruginosa cells were incubated in medium with peptides at different concentrations, and then the assays of viability, pyocyanin, elastase activity and biofilm formation of P. aeruginosa were performed. We found that the concentration‐dependent antibactericidal activity and down‐regulating pyocyanin, elastase and biofilm formation of LFchimera were significantly stronger than those of LF, LFcin, LFampin or LFcin plus LFampin. Conclusions: Our results indicated that LF, LFcin, LFampin and LFchimera were potential candidates to combat P. aeruginosa, and LFchimera was the most effective in them. Significance and Impact of the Study: The new LFchimera has better activity against P. aeruginosa than LF, LFcin and LFampin and may be a promising new compound for treatment of P. aeruginosa infection.     

Plant original Massilia isolates producing polyhydroxybutyrate, including one exhibiting high yields from glycerol

Aims: The purpose of this study was to isolate new and potentially better polyhydroxyalkanoate (PHA)‐producing bacteria, with a view to obtaining high yields from inexpensive substrates like glycerol, a major by‐product of the biodiesel process. Methods and Results: Eleven new plant original isolates of the genus Massilia, a poorly studied lineage within the Betaproteobacteria, were isolated and characterized. Two isolates, 2C4 and 4D3c, could not be assigned to a validated Massilia species and probably represent new species. Six isolates were found to produce poly‐3‐hydroxybutyrate (P3HB) when cultured with glucose or glycerol as carbon source. Isolate 4D6 accumulated up to 50 wt% of cell mass as polyhydroxybutyrate (PHB) when grown on glycerol. Conclusions: The phyllosphere may be a good source of bacteria unrelated or weakly related to human/animal pathogens for screening for new PHA producers for industrial application. Isolate 4D6 was capable of accumulating particularly high levels of PHB from glycerol. Significance and Impact of the Study: With the increase in biodiesel production, which generates increasing amounts of glycerol as a by‐product, there is a major interest in exploiting this compound as feedstock for the synthesis of interesting products, like biopolymers, such as PHA. The new Massilia sp. 4D6 isolate described in this study may be a useful candidate as a cell factory for the industrial production of PHA from glycerol.     

Characterization of polyhydroxyalkanoates accumulated by a moderately halophilic salt pan isolate Bacillus megaterium strain H16

Aim

Characterization of polyhydroxyalkanoates (PHA) accumulated by halophilic bacteria isolated from solar salterns.

Methods and Results

Twenty‐six halophilic isolates were obtained from solar salterns of Goa, India. They were screened for accumulation of PHA by Sudan black B, Nile blue A and Nile red stains. Strains H15, H16 and H26 were selected based on their intensity of Nile blue A/Nile red fluorescence. On the basis of phenotypic and genotypic characterization, the three isolates were identified as Bacillus megaterium. Growth kinetics and polymer accumulating capacity of strain H16 were studied in E2 mineral media with 2% glucose with/without NaCl. In the absence of NaCl, strain H16 accumulated PHA to 40·0% (w/w) of cell dry weight (CDW) at 42 h of growth, whereas in presence of 5% w/v NaCl, the culture showed longer lag phase of up to 24 h and accumulated a maximum PHA of 39% (w/w) CDW at 54 h of growth. The infrared spectra of both the polymers exhibited peaks at 1733·9 cm^?1 characteristic of C=O. Scans of ¹H nuclear magnetic resonance (NMR) showed a doublet at 2·5 ppm corresponding to methylene group (‐CH₂), the signal at 5·3 ppm corresponded to methine group (‐CH‐), and another signal at 1·3 ppm corresponded to the methyl group (‐CH₃). Scans of ¹³C NMR showed prominent peaks at 20, 40, 67–68 and 170 ppm, indicating the polymer to be homopolymer of 3‐hydroxybutyrates. The polymer is stable up to a temperature of 160°C.

Conclusion

Three moderately halophilic isolates (strain H15, H16 and H26) capable of accumulating PHA were isolated from solar salterns of Ribandar Goa, India, and identified as B. megaterium based on phenotypic and genotypic characterization. Strain H16 accumulated polyhydroxybutyrate in the presence and absence of NaCl up to 40% of its CDW.

Significance and Impact of the Study

This strain would be better suited for production of PHA at industrial level due to its tolerance to high concentration of NaCl.     

Hartmanella vermiformis can be permissive for Pseudomonas aeruginosa

Aims: The amoebae of the genus Hartmanella are frequently recovered from hospital water taps, whereas Pseudomonas aeruginosa is often implicated in nosocomial infections. Previous works suggested that free living amoebae can act as vehicles of bacterial transmission. The present work investigates the relationships between a strain of Hartmanella vermiformis and three strains of P. aeruginosa: a reference strain, a strain from a patient and an environmental strain. Methods and Results: In a saline medium, H. vermiformis is not able to favour for the development of P. aeruginosa. In a rich co‐cultivation medium, only the environmental strain has shown a growth. Conclusions: We showed that P. aeruginosa is not a good nutrient source for H. vermiformis. Significance and Impact of the Study: Nevertheless, in particular conditions and with particular strains, the presence of H. vermiformis could represent a possibility of growth for P. aeruginosa.     

Expression and characterization of (<Emphasis Type="Italic">R</Emphasis>)-specific enoyl coenzyme A hydratases making a channeling route to polyhydroxyalkanoate biosynthesis in <Emphasis Type="Italic">Pseudomonas putida</Emphasis>

We investigated the expression of (R)-specific enoyl coenzyme A hydratase (PhaJ) in Pseudomonas putida KT2440 accumulating polyhydroxyalkanoate (PHA) from sodium octanoate in order to identify biosynthesis pathways of PHAs from fatty acids in pseudomonads. From a database search through the P. putida KT2440 genome, an additional phaJ gene homologous to phaJ4 _Pa from Pseudomonas aeruginosa, termed phaJ4 _Pp, was identified. The gene products of phaJ1 _Pp, which was identified previously, and phaJ4 _Pp were confirmed to be functional in recombinant Escherichia coli on PHA synthesis from sodium dodecanoate. Cytosolic proteins from P. putida grown on sodium octanoate were subjected to anion exchange chromatography and one of the eluted fractions with hydratase activity included PhaJ4_Pp, as revealed by western blot analysis. These results strongly suggest that PhaJ4_Pp forms a channeling route from β-oxidation to PHA biosynthesis in P. putida. Moreover, the substrate specificity of PhaJ1_Pp was suggested to be different from that of PhaJ1_Pa from P. aeruginosa although these two proteins share 67% amino acid sequence identity.     

New insights in the formation of polyhydroxyalkanoate granules (carbonosomes) and novel functions of poly(3‐hydroxybutyrate)

The metabolism of polyhydroxybutyrate (PHB) and related polyhydroxyalkanoates (PHAs) has been investigated by many groups for about three decades, and good progress was obtained in understanding the mechanisms of biosynthesis and biodegradation of this class of storage molecules. However, the molecular events that happen at the onset of PHB synthesis and the details of the initiation of PHB/PHA granule formation, as well as the complex composition of the proteinaceous surface layer of PHB/PHA granules, have only recently come into the focus of research and were not reviewed yet. In this contribution, we summarize the progress in understanding the initiation and formation of the PHA granule complex at the example of Ralstonia eutropha H16 (model organism of PHB‐accumulating bacteria). Where appropriate, we include information on PHA granules of Pseudomonas putida as a representative species for medium‐chain‐length PHA‐accumulating bacteria. We suggest to replace the previous micelle mode of PHB granule formation by the Scaffold Model in which the PHB synthase initiation complex is bound to the bacterial nucleoid. In the second part, we highlight data on other forms of PHB: oligo‐PHB with ≈100 to 200 3‐hydroxybutyrate (3HB) units and covalently bound PHB (cPHB) are unrelated in function to storage PHB but are presumably present in all living organisms, and therefore must be of fundamental importance.     

Metformin prevents the effects of Pseudomonas aeruginosa on airway epithelial tight junctions and restricts hyperglycaemia‐induced bacterial growth

Lung disease and elevation of blood glucose are associated with increased glucose concentration in the airway surface liquid (ASL). Raised ASL glucose is associated with increased susceptibility to infection by respiratory pathogens including Staphylococcus aureus and Pseudomonas aeruginosa. We have previously shown that the anti‐diabetes drug, metformin, reduces glucose‐induced S. aureus growth across in vitro airway epithelial cultures. The aim of this study was to investigate whether metformin has the potential to reduce glucose‐induced P. aeruginosa infections across airway epithelial (Calu‐3) cultures by limiting glucose permeability. We also explored the effect of P. aeruginosa and metformin on airway epithelial barrier function by investigating changes in tight junction protein abundance. Apical P. aeruginosa growth increased with basolateral glucose concentration, reduced transepithelial electrical resistance (TEER) and increased paracellular glucose flux. Metformin pre‐treatment of the epithelium inhibited the glucose‐induced growth of P. aeruginosa, increased TEER and decreased glucose flux. Similar effects on bacterial growth and TEER were observed with the AMP activated protein kinase agonist, 5‐aminoimidazole‐4‐carboxamide ribonucleotide. Interestingly, metformin was able to prevent the P. aeruginosa‐induced reduction in the abundance of tight junction proteins, claudin‐1 and occludin. Our study highlights the potential of metformin to reduce hyperglycaemia‐induced P. aeruginosa growth through airway epithelial tight junction modulation, and that claudin‐1 and occludin could be important targets to regulate glucose permeability across airway epithelia and supress bacterial growth. Further investigation into the mechanisms regulating metformin and P. aeruginosa action on airway epithelial tight junctions could yield new therapeutic targets to prevent/suppress hyperglycaemia‐induced respiratory infections, avoiding the use of antibiotics.     

Recovery of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) from Ralstonia eutropha cultures with non‐halogenated solvents

Reduced downstream costs, together with high purity recovery of polyhydroxyalkanoate (PHA), will accelerate the commercialization of high quality PHA‐based products. In this work, a process was designed for effective recovery of the copolymer poly(hydroxybutyrate‐co‐hydroxyhexanoate) (P(HB‐co‐HHx)) containing high levels of HHx (>15 mol%) from Ralstonia eutropha biomass using non‐halogenated solvents. Several non‐halogenated solvents (methyl isobutyl ketone, methyl ethyl ketone, and butyl acetate and ethyl acetate) were found to effectively dissolve the polymer. Isoamyl alcohol was found to be not suitable for extraction of polymer. All PHA extractions were performed from both dry and wet cells at volumes ranging from 2 mL to 3 L using a PHA to solvent ratio of 2% (w/v). Ethyl acetate showed both high recovery levels and high product purities (up to 99%) when using dry cells as starting material. Recovery from wet cells, however, eliminates a biomass drying step during the downstream process, potentially saving time and cost. When wet cells were used, methyl isobutyl ketone (MIBK) was shown to be the most favorable solvent for PHA recovery. Purities of up to 99% and total recovery yields of up to 84% from wet cells were reached. During polymer recovery with either MIBK or butyl acetate, fractionation of the extracted PHA occurred, based on the HHx content of the polymer. PHA with higher HHx content (17–30 mol%) remained completely in solution, while polymer with a lower HHx content (11–16 mol%) formed a gel‐like phase. All PHA in solution could be precipitated by addition of threefold volumes of n‐hexane or n‐heptane to unfiltered PHA solutions. Effective recycling of the solvents in this system is predicted due to the large differences in the boiling points between solvent and precipitant. Our findings show that two non‐halogenated solvents are good candidates to replace halogenated solvents like chloroform for recovery of high quality PHA. Biotechnol. Bioeng. 2013; 110: 461–470. © 2012 Wiley Periodicals, Inc.     

Pseudomonas aeruginosa infection stimulates mitogen‐activated protein kinases signaling pathway in human megakaryocytes

Pseudomonas aeruginosa is a major cause of nosocomial infections and contributes to higher mortality in hospitalized individuals. Infection by P. aeruginosa triggers host immune response through activation of pathogen recognition receptors, which are present in innate cells. Several studies have reported the mechanism of P. aeruginosa induced innate immunity in multiple cell types. But so far there is no reports on response of megakaryocytes to P. aeruginosa infection. Hence, our aim was to investigate the precise role and signaling mechanism of megakaryocytes during P. aeruginosa infection. In this study, we used Mo7e cells as representatives of human megakaryocyte and found that P. aeruginosa infection induces cytotoxicity in these cells. We further demonstrated that P. aeruginosa infection modulates p38 and extracellular signal regulated kinase pathways in Mo7e cells. Protein expression profiling in P. aeruginosa lipopolysaccharide‐treated Mo7e cells revealed upregulation of importin subunit β and downregulation of metabolic enzymes. Our results suggest that P. aeruginosa infection regulates mitogen‐activated protein kinases signaling pathway and importin in Mo7e cells and that this is a potential mechanism for nuclear translocation of nuclear factor binding near the κ light‐chain gene in B cells and c‐Jun N‐terminal kinases to induce cell cytotoxicity.     

Characterization of Pseudomonas aeruginosa phage KPP21 belonging to family Podoviridae genus N4‐like viruses isolated in Japan

Bacteriophages (phages) belonging to the family Podoviridae genus N4‐like viruses have been used as therapeutic agent in phage therapy against Pseudomonas aeruginosa infections. P. aeruginosa phage KPP21 was isolated in Japan, and phylogenetically investigated the phages belonging to this viral genus. Morphological and genetic analyses confirmed that phage KPP21 belongs to the family Podoviridae genus N4‐like viruses. Moreover, phylogenetic analyses based on putative DNA polymerase and major virion protein showed that P. aeruginosa phages belonging to the genus N4‐like viruses are separated into two lineages and that phage KPP21 is in the same clade as phage LUZ7.     

Comparative bioelectrochemical analysis of Pseudomonas aeruginosa and Escherichia coli with anaerobic consortia as anodic biocatalyst for biofuel cell application

Aims: To study the bioelectrochemical behaviour of Pseudomonas aeruginosa (MTCC 17702) and Escherichia coli (MTCC 10436) and to assess their potential to act as anodic biocatalyst with the function of anaerobic consortia for microbial (bio) fuel cell (BFC) application. Methods and Results: Three BFCs (single chamber; open‐air cathode; noncatalysed electrodes) were operated simultaneously in acidophilic microenvironments. Pseudomonas aeruginosa (BFC_P) showed higher current density (264 mA m^?2) followed by mixed culture (BFC_M; 166 mA m^?2) and E. coli (BFC_E; 147 mA m^?2). However, total operating period and substrate degradation were relatively found to be effective with mixed culture (58%; 72 h) followed by BFC_P (39%; 60 h) and BFC_E (31%; 48 h). Higher electron discharge (ED) was observed with Ps. aeruginosa while mixed culture showed the involvement of redox mediators in the ED process. Conclusions: Mixed culture showed to sustain biopotential for longer periods along with a stable ED. The presence of redox signals and high substrate degradation was also evidencing its performance compared to the pure strains studied. This supports the practical utility of mixed culture over the pure cultures for real‐field BFC applications especially while operating with wastewater. Significance and Impact of the Study: This study revealed the efficiency and viability of mixed consortia in comparison with pure strains for microbial (bio) fuel cell applications.