Pseudomonas Psychrophila Research Articles

Metagenomic Analysis to Assess the Impact of Plant Growth-Promoting Rhizobacteria on Peanut (Arachis hypogaea L.) Crop Production and Soil Enzymes and Microbial Diversity.

Peanut production could be increased through plant growth-promoting rhizobacteria (PGPR). In this regard, the present field research aimed at elucidating the impact of PGPR on peanut yield, soil enzyme activity, microbial diversity, and structure. Three PGPR strains (Bacillus velezensis, RI3; Bacillus velezensis, SC6; Pseudomonas psychrophila, P10) were evaluated, along with Bradyrhizobium japonicum (BJ), taken as a control. PGPR increased seed yield by 8%, improving the radiation use efficiency (4-14%). PGPR modified soil enzymes (fluorescein diacetate activity by 17% and dehydrogenase activity by 28%) and microbial abundance (12%). However, PGPR did not significantly alter microbial diversity; nonetheless, it modified the relative abundance of key phyla (Actinobacteria > Proteobacteria > Firmicutes) and genera (Bacillus > Arthrobacter > Pseudomonas). PGPRs modified the relative abundance of genes associated with N-fixation and nitrification while increasing genes related to N-assimilation and N-availability. PGPR improved agronomic traits without altering rhizosphere diversity.

Metagenomics insights into the microbial resistome and virulome composition of Kampala’s wastewater

Background Antimicrobial-resistant (AMR) infections represent a major global health threat, causing approximately 700,000 deaths each year directly due to AMR-related issues worldwide. In Africa, 42.6% of countries lack sufficient data on AMR, highlighting a crucial gap in our reports. Consequently, there's a pressing need for thorough AMR surveillance data. Urban sewage, harboring a diverse array of microbes from sizable and mostly healthy populations, offers an excellent sampling opportunity. This study set out to identify and assess the microbes present in urban sewage in Kampala, while also analyzing the microbial resistome and virulome associated with urban sewage. Methods Samples were gathered from two wastewater treatment facilities, capturing data from both wet and dry seasons to reflect population behavior across seasons. DNA was extracted from these samples and underwent shotgun metagenomics sequencing. The resulting FastQ files were analyzed using a tailored metagenomics approach to identify microbial profiles, antibiotic-resistant genes, and virulence factors. Results In the pathobiome examined, Pseudomonas psychrophila, a fish pathogen, was the most prevalent, while Klebsiella pneumoniae was the least prevalent. Analysis identified 23 resistant genes, primarily conferring resistance to tetracyclines. Additionally, 29 virulence factors were identified, with a predominant association with bacterial motility. Notably, all of these virulence factors were found within Pseudomonas aeruginosa strain PAO1. Conclusion The utilization of shotgun metagenomics in sewage analysis is crucial for ongoing monitoring of microbial diversity and antimicrobial resistance. This approach uncovers intricate details that would be challenging or costly to obtain through conventional methods like PCR and culture-based techniques.

Plant Growth Promoting Rhizobacteria (PGPR): Impact on peanut flowering, seed physical quality, and yield determination (Arachis hypogaea L.)

Peanut seed yield is influenced by physiological and ecophysiological crop traits, with changes in reproductive parameters such as flowering time, flower number, and fertility index significantly affecting productivity. Management practices like Plant Growth-Promoting Rhizobacteria (PGPR) could enhance crop yield. PGPR can improve flowering and yield by modulating the balance of phytohormones and enhancing reproductive processes. This study assessed PGPR effects on peanut flowering dynamics, seed yield determination, and correlation with hormone levels. Two plant-level field experiments were conducted during 2019–2020 and 2020–2021, sowing two cultivars (ASEM 400 INTA and Granoleico) on four sowing dates (Oct-05, Oct-15, Nov-29, Dec-10). Three PGPR strains (Bacillus velezensis RI3 and SC6, Pseudomonas psychrophila P10), Bradyrhizobium japonicum, and control were arranged in a split-split-split-plot design, with sowing dates as main plots, cultivars as sub-plots, and PGPRs as sub-sub-plots. PGPR improved peanut flower number (FN) and flowering rate (FR) by 20 % and 50 % compared to B. japonicum and the control. B. velezensis SC6 showed the best performance (SC6 > P10 > RI3), advancing the flowering peak by 4–12 days. PGPR also increased the fertility index (FI) to 0.31 vs. 0.24 of B. japonicum and control and pod number (PN) by 53 % compared to the control. Flowering peak advancement led to larger seeds (SF≥8 mm) (∼+8 % vs. control) due to better environmental conditions (i.e., higher temperatures). Seed number (SN) increased by 94 %–113 % under PGPR treatments. Seed yield (SY) was increased (∼75 % on average) due to higher total biomass (TB) production and improved carbon allocation to seeds (harvest index; 0.33–0.36). Hormone analysis at the R5 stage under late sowing's restrictive conditions showed hormone level increases of 15 %–90 %. This study demonstrates that PGPR significantly improves peanut flowering dynamics, seed quality, and yield by affecting hormone levels and reproductive parameters, highlighting its potential as a sustainable management practice.

Insights into the fish protein degradation induced by the fish-borne spoiler Pseudomonas psychrophila and Shewanella putrefaciens: From whole genome sequencing to quality changes

The aim of this study is evaluating the protein degradation capacity of specific spoilage organisms (SSOs) Pseudomonas psychrophila and Shewanella putrefaciens in fish flesh during chilled storage and revealing the underlying genes by whole-genome sequencing (WGS). Biochemical and physical tests were performed on fish flesh inoculated with P. psychrophila and S. putrefaciens individually, including textural properties, myofibrillar fragmentation index, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles, free amino acid composition, total volatile basic nitrogen (TVB-N), trichloroacetic acid (TCA) soluble peptides, and muscle microstructure. Results showed that P. psychrophila and S. putrefaciens exhibited a strong capacity for decomposing the fish protein, and the deterioration of fish flesh texture was primarily attributed to P. psychrophila. The genes from SSOs associated with the production of proteases were identified by whole genome sequencing and serine protease may be the primary enzyme secreted by SSOs involved in the degradation of fish protein. Therefore, the present study has shed light on the mechanisms of protein degradation induced by SSOs, thereby offering valuable insights for the development of effective quality control strategies.

Enzymase Activity of Gut Microbes Isolated from the Rugose Spiraling Whitefly Aleurodicus rugioperculatus

This study investigated the enzymatic diversity among various bacterial isolates of Rugose Spiraling Whitefly (Aleurodicus rugioperculatus), shedding light on their potential industrial applications. Notably, Bacillus cereus (MRSW01) exhibited remarkable amylase and lipase activities, aligning with its reputation as a prominent amylase producer. These enzymes are crucial in the food industry, particularly in starch and lipid degradation processes. Pseudomonas helleri (CHRSW028) demonstrated substantial cellulase activity, essential for breaking down cellulose in plant materials, suggesting its relevance in biofuel production and waste management. Pseudomonas psychrophila (CRSW024) stood out with the highest pectinase and significant lipase activities, both of which find applications in the food and textile industries and the hydrolysis of fats and oils, respectively. Proteus vulgaris strains MRSW05 and CHRSW02 displayed significant amylase, cellulase, and protease activities, making them versatile candidates for various industrial applications, including detergent formulations and bioremediation processes. Conversely, Hafnia paralvei exhibited comparatively lower enzymatic activities, indicating limited industrial potential. The rich enzymatic diversity within these bacterial isolates and highlight their potential contributions to various industrial sectors, ranging from food and textiles to biofuel production and waste management. Such insights can inform the development of biotechnological applications and processes, ultimately benefitting both industrial and environmental domains.

Identificación de las bacterias intestinales de la polilla de la cera mayor

Throughout the world, the use of industrial polymers derived from fossil fuels is practically inevitable because they have such a wide range of applications; however, the environmental problems arising from this practice have led to a search for alternatives which will allow their use to be reduced, as well as strategies for their control by degradation using biorganic active agents. Insects have been a focus of special interest, as some species consume plastics and may serve to biodegrade them through the action of bacteria in their digestive tracts. In this context, the object of the present study was to characterise bacteria present in the intestine of wax moth larvae (Galleria mellonella). Thirty larvae were subjected to a diet based on polystyrene foam and thirty larvae in natural diet for 7 days. Gastrointestinal tracts were extracted and PCR was run. The results showed the presence of bacterial cells of Carnobacterium maltaromaticum, Brevibacterium sandarakinum, Pseudomonas psychrophila, Pseudomonas sp., Providence sp., Corynebacterium sp. However, the real action of these groups of bacteria in the effective degradation of polymers must be verified.

Transcriptomics and proteomics revealed the psychrotolerant and antibiotic-resistant mechanisms of strain Pseudomonas psychrophila RNC-1 capable of assimilatory nitrate reduction and aerobic denitrification

Aerobic denitrification has been proved to be profoundly affected by temperature and antibiotics, but little is known about how aerobic denitrifiers respond to temperature and antibiotic stress. In this study, the nitrate reduction performance and the intracellular metabolism by a psychrotolerant aerobic denitrifying bacteria, named Pseudomonas psychrophila RNC-1, were systematically investigated at different temperatures (10 °C, 20 °C, 30 °C) and different sulfamethoxazole (SMX) concentrations (0 mg/L, 0.1 mg/L, 0.5 mg/L, 1.0 mg/L, and 5.0 mg/L). The results showed that strain RNC-1 performed satisfactory nitrate removal at 10 °C and 20 °C, but its growth was significantly inhibited at 30 °C. Nitrate removal by strain RNC-1 was slightly promoted in the presence of 0.5 mg/L SMX, whereas it was significantly suppressed with 5.0 mg/L SMX. Nitrogen balance analysis indicated that assimilatory nitrate reduction and dissimilatory aerobic denitrification jointly dominated in the nitrate removal process of strain RNC-1, in which the inhibition effected on assimilation process was much higher than that on the aerobic denitrification process under SMX exposure. Further transcriptomics and proteomics analysis revealed that the psychrotolerant mechanism of strain RNC-1 could be attributed to the up-regulation of RNA translation, energy metabolism, ABC transporters and the over-expression of cold shock proteins, while the down-regulation of oxidative phosphorylation pathway was the primary reason for the deteriorative cell growth at 30 °C. The promotion of nitrate reduction with 0.5 mg/L SMX was related to the up-regulation of amino acid metabolism pathways, while the down-regulation of folate cycle, glycolysis/gluconeogenesis and bacterial chemotaxis pathways were responsible for the inhibition effect at 5.0 mg/L SMX. This work provides a mechanistic understanding of the metabolic adaption of strain RNC-1 under different stress, which is of significance for its application in nitrogen contaminated wastewater treatment processes.

Effect of black pepper essential oil on quorum sensing and efflux pump systems in the fish-borne spoiler Pseudomonas psychrophila KM02 identified by RNA-seq, RT-qPCR and molecular docking analyses

Given the increasing consumption of aquatic foods and green consumerism, efficient methods for extending the shelf-life and maintaining the safety of seafood are urgently required. The present study aimed to evaluate the effect of black pepper essential oil (BPEO) and its major compounds – limonene (LIM) and beta-caryophyllene (CAR) on quorum sensing (QS) and efflux pump (EP) systems in Pseudomonas psychrophila KM02. Transcriptomic analysis was performed to select antimicrobial resistance genes that were only truly expressed within the system mimicking the food matrices. Compounds analyzed at subinhibitory concentrations (subMICs) (135, 65 and 35 μL/mL) reduced QS autoinducer synthesis to levels lower than the limit of detection and decreased proteolytic activity and exopolysaccharide synthesis by 35, 29 and 28%, and by 58, 32 and 41%, respectively. These phenotypic results were confirmed by changes in the ratio of expression of selected genes. Furthermore, the anti-QS activity and anti-EP of LIM and CAR were evaluated by molecular docking analyses with QS receptor proteins (LasR, RhlR, TraR, and PqsR) and inner membrane EP proteins (MuxB, MexB, and Mfs). The mRNA transcript levels of membrane fusion and outer membrane proteins, and transcription of repressor regulators MarR and TetR were considerable decreased. Our work showed that BPEO major compounds affected the functioning of the QS and EP system in KM02 and consequently reduced the spoilage potential.

Introduce of Pseudomonas psychrophila, as a new Pathogen Causing Disease in Cultured Rainbow trout (Oncorhynchus mykiss)

Introduce of Pseudomonas psychrophila, as a new Pathogen Causing Disease in Cultured Rainbow trout (Oncorhynchus mykiss)

Carbonate biomineralization differentially induced by two psychrophilic Pseudomonas psychrophila strains isolated from an alpine travertine landform.

Besides geography and climate, biological factors play an important role in shaping travertine landforms, but the biochemical mechanisms of microbial processes in travertine formation have been rarely studied. Two psychrophilic bacterial strains, A20-18 and B21-3 of Pseudomonas psychrophila, isolated from travertine pools of Huanglong, a typical alpine travertine landform, were investigated for their roles in calcium carbonate mineralization, including the deposition process and products. X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy were used to characterize the crystal phase and morphology of CaCO3 precipitation. The results showed that there were no significant differences between the two strains in CaCO3 deposition rate. Extracellular polymeric substances (EPS)-free cells significantly inhibited calcification, compared with a control. Irregular crystals and polyhedral structures are common to all treatments using the two strains. These complex polycrystals were the result of the synergistic effect of homogeneous nucleation and heterogeneous nucleation. EPS and cells of strain B21-3 formed ring-like structures of calcium carbonate, which was possibly from the amphiphilic polymer forming a circular arrangement in water. These results are significant for understanding the microbial factor in Huanglong travertine deposition and providing new insights into the morphological control of the biomineralization mechanism at low temperatures.

Bacterial-fungal interactions revealed by genome-wide analysis of bacterial mutant fitness.

Microbial interactions are expected to be major determinants of microbiome structure and function. Although fungi are found in diverse microbiomes, their interactions with bacteria remain largely uncharacterized. In this work, we characterize interactions in 16 different bacterial-fungal pairs, examining the impacts of 8 different fungi isolated from cheese rind microbiomes on 2 bacteria (Escherichia coli and a cheese-isolated Pseudomonas psychrophila). Using random barcode transposon site sequencing (RB-TnSeq) with an analysis pipeline that allows statistical comparisons between different conditions, we observed that fungal partners caused widespread changes in the fitness of bacterial mutants compared to growth alone. We found that all fungal species modulated the availability of iron and biotin to bacterial species, suggesting that these may be conserved drivers of bacterial-fungal interactions. Species-specific interactions were also uncovered, a subset of which suggest fungal antibiotic production. Changes in both conserved and species-specific interactions resulted from deletion of a global regulator of fungal specialized metabolite production. This work highlights the potential for broad impacts of fungi on bacterial species within microbiomes.

Pathogenic Fungi and Bacteria from Homogenates and Commercial Beverages of <i>Auricularia polytricha</i>

Auricularia polytricha is an important edible and medicinal fungus in Taiwan. The cultivation environment and sterilization of the mushroom cultivation bag before cultivation may affect the fungal species that occur along the fruiting body for Mucor irregularis, M. fusiformis, and Trichoderma longibrachiatum and the stalk, for Hypocrea koningii, Rhodotorula mucilaginosa, and Coprinellus radians from the stalk. The bacterial species associated with A. polytricha were also identified by PCR amplification, PCR-RFLP analysis, sequencing and BLASTn analysis. Bacterial species were identified as Bacillus cereus, Pseudomonas tolaasii, Sphingomonas paucimobilis, Acinetobacter pittii, and Lysinibacillus fusiformis in the homogenates after Pasteur sterilization. During a flavor test of 11 commercial drinks, the testers reported experiencing diarrhea. Bacterial examination of the drinks found that three samples were contaminated. Five bacterial species were identified as Pantoea agglomerans, Serratia liquefaciens, and Pseudomonas psychrophila in sample 275, Cronobacter sakazakii and Pseudomonas azotoformans in sample 684 and Pseudomonas azotoformans in sample 539, and more than one bacterial species occurred in two samples. In conclusion, pathogenic fungal and bacterial species were obtained from the fruiting bodies, stalks, homogenates, and drinks of A. polytricha after Pasteur sterilization. To prevent foodborne diseases from A. polytricha, sanitation procedures should be enforced during cultivation, processing and post-harvest storage.

Deciphering the Cold Adaptive Mechanisms in Pseudomonas psychrophila MTCC12324 Isolated from the Arctic at 79° N.

Psychrophiles, host of cold environments, have been successfully undergoing the process of evolution by which they have acquired innate adaptations to withstand the unfavorable effects of low temperature. Psychrophiles renders immense opportunity to explore the underlying mechanisms of cold adaptation. The present study focused to explore the cold adaptive mechanisms of Pseudomonas psychrophila MTCC12324, a facultative psychrophilic bacterium isolated from the Ny-Alesund, an island in the Svalbard Archipelago (79°55' N, 11°56' E) in the Arctic. Whole genome sequencing of P. psychrophila MTCC12324 and its analysis revealed the redundant nature of genome and identified several cold acclimation genes including cold shock proteins, and chaperones involved in the adaptive mechanism to thrive in the cold environment. Comparative proteome analysis of P. psychrophila MTCC12324 at 4°C and 25°C has thrown lights on the metabolic pathways and cellular processes adopted to withstand the cold environment. Basic survival pathways and factors involved in energy metabolism were found to be unaltered whereas stress response factors, enzymes involved in fatty acid elongation and cold-adapted chaperones were found to be enhanced towards cold stress. The present study facilitates recognition of crucial factors including polyunsaturated fatty acid biosynthesis, mRNA chaperones, and other cold-inducible proteins which favors the bacteria in conferring cold adaptation.

Analysis of amino acid residues involved in the thermal properties of isocitrate dehydrogenases from a psychrophilic bacterium, Colwellia maris, and a psychrotrophic bacterium, Pseudomonas psychrophila

Monomeric NADP+-dependent isocitrate dehydrogenase (IDH) from a psychrophilic bacterium, Colwella maris, (CmIDH) is a cold-adapted enzyme, whereas that of a psychrotrophic bacterium, Pseudomonas psychrophila, (PpIDH) is mesophilic. However, the amino acid sequence identity of the two IDHs is high (67%). To identify the amino acid residues involved in the differences in their thermal properties, such as optimum temperature and thermostability for activity, six amino acid residues located in the corresponding positions of their regions 2 and 3 were substituted by site-directed mutagenesis, and several thermal properties of the mutated IDHs were examined. CmIDH mutants, CmE538L, CmE596L and CmA741S, substituted at Glu538, Glu596 and Ala741 by the corresponding PpIDH residues of Leu, Leu and Ser, respectively, exhibited higher thermostability than wild-type CmIDH (CmWT). Furthermore, the specific activity of CmE596L and CmA741S was higher than that of CmWT. On the other hand, the corresponding mutants of PpIDH PpL536E, PpL594E and PpS739A were more thermolabile than wild-type PpIDH, and PpL594E had a lower specific activity at temperatures over 45°C. These results suggested that these amino acid residues of CmIDH and PpIDH are involved in their thermal properties.

Biochemical changes induced by dominant bacteria in chill-stored silver carp (Hypophthalmichthys molitrix) and GC-IMS identification of volatile organic compounds

To evaluate the spoilage potential of dominant bacteria (Aeromonas allosaccharophila, Pseudomonas psychrophila, and Shewanella putrefaciens) isolated from spoiled silver carp (Hypophthalmichthys molitrix) fillets, biochemical changes including protein degradation, trichloroacetic acid (TCA)-soluble peptides, total volatile basic nitrogen (TVB-N), biogenic amines, nucleotide catabolism, and volatile organic compounds were examined in single-species inoculated silver carp flesh for 14 days at 4 °C. P. psychrophila exhibited the strongest proteolytic activity, which resulted in the highest concentrations of TCA-soluble peptides and TVB-N. S. putrefaciens was responsible for the production of putrescine and cadaverine and led to the fastest degradation of hypoxanthine riboside (HxR). At the end of storage, P. psychrophila was the main producer of ketones, especially the C7-C9 ketones, while sulfur compounds were released primarily by S. putrefaciens. Moreover, 1-propanol, butanone, 2-hexanone, methyl isobutyl ketone, dimethyl sulfide, and dimethyl disulfide increased gradually with storage time, suggesting their potential as spoilage markers for freshness/spoilage monitoring. P. psychrophila possessed the strongest spoilage potential in the fish matrix, followed by S. putrefaciens, whereas A. allosaccharophila showed a very low spoilage potential. In conclusion, P. psychrophila and S. putrefaciens were identified as the specific spoilage organisms (SSOs) of silver carp, suggesting that preservation researchers should focus on these two spoilage contributors in future studies. This research contributes to a deeper understanding of silver carp spoilage and to the development of methods and tools to improve fish quality management.

Amplification of Raman spectra by gold nanorods combined with chemometrics for rapid classification of four Pseudomonas

This paper demonstrates the application of surface-enhanced Raman scattering (SERS) using positive charged gold nanorods (Au NRs) as an enhancement substrate to classify Pseudomonas spp. coupled with multivariate methods. Four species of Pseudomonas as dominant spoilage bacteria of food were isolated from rotten chicken, namely, Pseudomonas gessardii (P9), Pseudomonas psychrophila (P8), Pseudomonas psychrophila (S2) and Pseudomonas fluorescens (T3). Au NRs were synthesized with positive charge by seed-mediated growth method which can be adsorbed onto the surface of the bacteria by electrostatic adsorption. SERS spectra were collected individually for four types of Pseudomonas and pretreated by mean centering (MC), then principal component analysis (PCA) and hierarchical clustering analysis (LDA) were used to achieve data dimensionality reduction and visualize the result of differentiation for the species of Pseudomonas. Particularly, the classification accuracy of LDA was reached to 100%. Following we applied hierarchical clustering analysis (HCA) to cluster each species of Pseudomonas and the results of HCA consistent with the results of 16S rRNA. This study has shown that SERS combined with LDA and HCA can be used as a reliable method to classify Pseudomonas.

Isolation and characterization of Pb-resistant plant growth promoting endophytic bacteria and their role in Pb accumulation by fast-growing trees

ABSTRACT Lead (Pb) contamination is one of the major environmental problems on a global scale. Bacterial endophytes have been accepted as a promising technique to assist phytoremediation. In this study, three Pb-tolerant endophytic bacteria were isolated from the roots of Pityrogramma calomelanos. Based on partial 16S rRNA gene sequencing analysis, all isolates were similar to Pseudomonas and tolerated Pb concentration up to 1850mg/L, producing siderophores and solubilized phosphate. Among them, Pc isolate closely related to Pseudomonas psychrophila showed the highest water-soluble Pb in solution (Pb solubilization) and in contaminated soil. This isolate was chosen to study the effects on Pb accumulation in the roots of Acacia mangium and Eucalyptus camaldulensis by a hydroponic experiment. The results showed that, in the Hoagland nutrient solution with no Pb spiking, the roots showed no significant difference (p > 0.05), and the concentration of Pb ranged from 10 to 89 mg/kg. In the nutrient solution in the presence of 30 mg/L Pb, there were no significant changes in Pb contents in roots. However, A. mangium showed an increase in Pb concentration in the roots (6829 ± 697 mg/kg), compared to non-inoculation (6242 ± 272 mg/kg). E. camaldulensis inoculation showed a decrease in Pb content (3763 ± 592 mg/kg), compared to non-inoculation (4233 ± 264 mg/kg). These results suggest that the Pc isolate closely related to P. psychrophila was effective in promoting the phytoremediation potential of A. mangium, but it was not useful for E. camaldulensis.

Spoilage Pseudomonas biofilm with Escherichia coli protection in fish meat at 5 °C.

Pseudomonas are part of the indigenous microbiota of different foods, where they gradually cause spoilage. In fish meat, Pseudomonas fragi and Pseudomonas psychrophila have been identified as important spoilers. The initial aim of this study was to investigate the physiological characteristics, adhesion, and biofilm of P. fragi and P. psychrophila under temperatures related to the fish-processing industry. The further aim was to define the problem of increased growth of pathogenic bacteria in the presence of spoilage bacteria in vitro and in fish meat. Temperature dependence on physiological characteristics, adhesion, and biofilm was observed. Hydrophobicity and autoaggregation were most prominent at 15 °C, and at this temperature floating biofilm was also formed. The adhesion of these Pseudomonas was up to 2 log CFU cm-1 more pronounced on stainless steel than polystyrene, with up to five times greater biofilm biomass production at 5 °C on polystyrene. This paralleled at least a 0.5 log CFU g-1 increase in the pathogenic bacterium Escherichia coli in fish meat. Pseudomonas fragi and P. psychrophila adhesion and biofilm depend on the temperature, and are stimulated by temperatures that can occur during the processing and storage of fish meat. Strong Pseudomonas biofilm formation under refrigeration conditions is protective for E. coli, potentially by providing more favorable conditions by ensuring a higher concentration of nutrients. Interactions between spoilage Pseudomonas and pathogenic bacteria can occur through different mechanisms, and an understanding of these is of particular importance to ensure the overall quality and safety of fish meat and other proteinaceous foods. © 2019 Society of Chemical Industry.

Contribution of Three Different Regions of Isocitrate Dehydrogenases from Psychrophilic and Psychrotolerant Bacteria to Their Thermal Properties.

Monomeric isocitrate dehydrogenases of a psychrophilic bacterium, Colwellia maris, and a psychrotolerant bacterium, Pseudomonas psychrophila, (CmIDH and PpIDH) are cold-adapted and mesophilic, respectively. On the other hand, previous studies revealed that the monomeric IDH of Azotobacter vinelandii (AvIDH) is also mesophilic and the regions 2 and 3 among three regions of this enzyme are involved in the thermal properties. Therefore, to examine whether the region(s) responsible for the mesophilic properties are common between PpIDH and AvIDH, the genes of chimeric IDHs exchanging three regions of PpIDH and CmIDH in various combinations were constructed and overexpressed as His-tagged recombinant proteins in the Escherichia coli cells, and the chimeric and wild-type PpIDH and CmIDH were purified with Ni-chelating affinity column chromatography. The swapping chimeras of the regions 2 or 3 in PpIDH and CmIDH showed lower and higher optimum temperatures for activities and their thermostabilities than the wild-type ones, respectively. On the other hand, the exchange of the respective region 1 hardly influenced these properties of the two IDHs. Therefore, the regions 2 and 3 of the two IDHs were confirmed to be involved in their thermal properties. These results were coincident with those of the previous study on chimeric IDHs between AvIDH and CmIDH, indicating that the common regions of AvIDH and PpIDH are responsible for their mesophilic properties and the amino acid residues involved in their thermal properties are present in the regions 2 and 3.

Rapid Pseudomonas Species Identification from Chicken by Integrating Colorimetric Sensors with Near-Infrared Spectroscopy

Pseudomonas spp. are the dominant spoilage bacteria which can cause chicken spoilage. Some traditional detection methods are often unsuitable for their rapid real-time detection. Thus, in this paper, a fusion strategy based on colorimetric sensors and near-infrared spectroscopy was applied to rapidly identify Pseudomonas spp. in chicken. First, four different species of Pseudomonas—Pseudomonas gessardii, Pseudomonas psychrophila, Pseudomonas fragi, and Pseudomonas fluorescens—were isolated from putrid chicken, and then, the odor and spectral information of the Pseudomonas species and their mixture were obtained by colorimetric sensors and near-infrared spectroscopy, respectively. Thirty-six odor characteristic variables and 33 spectral characteristic variables were extracted from each technique and used for data fusion based on principal component analysis (PCA). Back-propagation artificial neural network (BP-ANN) was used to build identification model for the discrimination of the different Pseudomonas species. The results showed that the discrimination capability of the model based on data fusion was superior to that based on the two techniques independently, and eventually BP-ANN achieved 100% classification rate by cross-validation and 98.75% classification rate in predication set. This work indicates that the combination of colorimetric sensors and near-infrared spectroscopy is promising for the rapid identification of Pseudomonas species in chicken extract, and hence may be applied towards quality monitoring.