Fluorescent Pseudomonas Species Research Articles

Bioinoculation with Pseudomonas aeruginosa P4 enhances the peanut root nodulation and nutrient status while enriching the plant-beneficial bacteria in rhizosphere

Fluorescent Pseudomonas species are well-known as effective plant growth promoting rhizobacteria (PGPR), yet are relatively less explored for their multitrophic benefits. This study demonstrates the impact of P. aeruginosa P4 (P4) on peanut growth, nutrient status of plant and soil as well as the rhizobacterial community. Enhanced root length (53%), root weight (74%) and shoot weight (48%) in P4-treated plants, with increased potash and phosphorus levels of rhizospheric soil, correlated with indole-3-acetic acid and organic acid producing abilities of P4. Remarkably, increased nodule (87%) and pod (47%) numbers in P4-treated plants could be attributed to ∼16.3 % higher accumulation of iron, which in turn could be due to siderophore producing ability of P4. Amplified Ribosomal DNA Restriction Analysis (ARDRA)-based analysis at the approximate onset of nodulation and subsequent 16S rDNA-based metagenomic analysis estimated a significant distinction in the rhizomicrobial community diversity and abundance across control and P4-treated rhizospheres, plausibly due to P4-induced alterations in root exudate composition. Enrichment of plant-beneficial genera like Planctomyces, Mesorhizobium, Ensifer, Azospirillum, Bacillus, Nitrospira and Candidatus Nitrososphaera in P4-treated rhizosphere, could be driven by both altered root exudation and enhanced mineral nutrient availability in soil. In contrast, reduced abundance of Pseudomonas genus in P4-treated peanut rhizosphere could be attributed to direct or indirect competition between the inoculant and the resident Pseudomonas species. Collectively, a non-nitrogen-fixer P4 benefited nitrogen fixation in peanut, apparently indirectly by improving the iron nutrition and mobilization of plant-beneficial rhizobacterial species; an aspect that could be useful in determining PGPR efficacy and strategizing PGPR-mediated rhizosphere engineering.

Unusual concurrence of P-solubilizing and biocontrol traits under P-limitation in plant-beneficial Pseudomonas aeruginosa P4: insights from in vitro metabolic and gene expression analysis.

Plant-beneficial fluorescent Pseudomonas species with concurrent P-solubilizing and biocontrol traits could have improved rhizospheric survival and efficacy; this rare ability being subject to diverse environmental and endogenous regulations. This study correlates growth patterns, time-course analysis of selected metabolites, non-targeted metabolomics of exometabolites and selected gene expression analysis to elucidate P-limitation-induced physiological shifts enabling co-production of metabolites implied in P-solubilization and biocontrol by P. aeruginosa P4 (P4). P-limited culture supernatants showed enhanced production of selected biocontrol metabolites such as pyocyanin, pyoverdine and pyochelin and IAA while maintaining biomass yield despite reduced growth rate and glucose consumption. Non-targeted exometabolomics further indicated that P-limitation positively impacted pentose phosphate pathway as well as pyruvate, C5-branched dibasic acid and amino acid metabolism. Its correlation with unusually reduced aroC expression and growth phase-dependent changes in the expression of key biosynthetic genes pchA, pchE, pchG, pvdQ and phzM implied a probable regulation of biosynthesis of chorismate-derived secondary metabolites, not neglecting the possibility of multiple factors influencing the gene expression profiles. Similar increase in biocontrol metabolite production was also observed in Artificial Root Exudates (ARE)-grown P4 cultures. While such metabolic flexibility could impart physiological advantage in sustaining P-starvation stress, it manifests as unique coexistence of P-solubilizing and biocontrol abilities.

Rapid identification of pyoverdines of fluorescent Pseudomonas spp. by UHPLC-IM-MS

Siderophores are iron-chelating molecules produced by bacteria and other microbes. They are involved with virulence in infections and play key roles in bacterial community assembly and as plant protectants due to their pathogen control properties. Although assays exist to screen whether newly isolated bacteria can produce siderophores, the chemical structures of many of these bio-active molecules remain unidentified due to the lack of rapid analytical procedures. An important group of siderophores are pyoverdines. They consist of a structurally diverse group of chromopeptides, whose amino acid sequence is characteristic for the fluorescent Pseudomonas species that secrets them. Although over 60 pyoverdine structures have been described so far, their characterization is cumbersome and several methods (isoelectrofocusing, iron uptake measurement, mass determination) are typically combined as ambiguous results are often achieved by a single method. Those additional experiments consume valuable time and resources and prevent high-throughput analysis. In this work, we present a new pyoverdine characterisation option by recording their collision cross sections (CCS) using trapped ion mobility spectrometry. This can be done simultaneously in combination with UHPLC and high-resolution MS resulting in a rapid identification of pyoverdines. The high specificity of CCS values is presented for 17 pyoverdines secreted by different Pseudomonas strains. The pyoverdine mass determination by full scan MS was supported by fragments obtained from broadband collision induced dissociation (bbCID). As iron contaminations in laboratories are not uncommon, CCS values of ferripyoverdines were also evaluated. Thereby, unusual and highly characteristic ion mobility patterns were obtained that are suitable as an alternative identification marker.

Biosynthetic Origin of Formylaminooxyvinylglycine and Characterization of the Formyltransferase GvgI.

4-Formylaminooxyvinylglycine (FVG) is an herbicidal and antibacterial nonproteinogenic amino acid produced by several strains of the Pseudomonas fluorescens species complex. It contains a unique vinyl alkoxyamine moiety with an O-N bond, and its biosynthetic origin remains unknown. Here, we show that the gvg cluster from P. fluorescens WH6 is responsible for the biosynthesis of FVG and two additional O-N bond-containing oxyvinylglycines, guanidinooxyvinylglycine and aminooxyvinylglycine. Feeding studies in the producing bacteria indicate that these compounds originate from homoserine. We identify a formyltransferase gvgI that is required for the production of FVG and characterize the activity of this enzyme in vitro toward amino acids with a side chain amine. Sequence similarity network analysis reveals that GvgI and homologues make up a distinct group from the main classes of formyltransferases.

Comparative genomic insights into the epidemiology and virulence of plant pathogenic pseudomonads from Turkey.

Pseudomonas is a highly diverse genus that includes species that cause disease in both plants and animals. Recently, pathogenic pseudomonads from the Pseudomonas syringae and Pseudomonas fluorescens species complexes have caused significant outbreaks in several agronomically important crops in Turkey, including tomato, citrus, artichoke and melon. We characterized 169 pathogenic Pseudomonas strains associated with recent outbreaks in Turkey via multilocus sequence analysis and whole-genome sequencing, then used comparative and evolutionary genomics to characterize putative virulence mechanisms. Most of the isolates are closely related to other plant pathogens distributed among the primary phylogroups of P. syringae, although there are significant numbers of P. fluorescens isolates, which is a species better known as a rhizosphere-inhabiting plant-growth promoter. We found that all 39 citrus blast pathogens cluster in P. syringae phylogroup 2, although strains isolated from the same host do not cluster monophyletically, with lemon, mandarin orange and sweet orange isolates all being intermixed throughout the phylogroup. In contrast, 20 tomato pith pathogens are found in two independent lineages: one in the P. syringae secondary phylogroups, and the other from the P. fluorescens species complex. These divergent pith necrosis strains lack characteristic virulence factors like the canonical tripartite type III secretion system, large effector repertoires and the ability to synthesize multiple bacterial phytotoxins, suggesting they have alternative molecular mechanisms to cause disease. These findings highlight the complex nature of host specificity among plant pathogenic pseudomonads.

Microbiological Safety and Sensory Quality of Cultivated Mushrooms (Pleurotus eryngii, Pleurotus ostreatus and Lentinula edodes) at Retail Level and Post-Retail Storage.

In this study, the microbiological and sensory quality of cultivated mushrooms (Pleurotus ostreatus and eryngii and Lentinula edodes) available at the Austrian retail level were determined. Aerobic mesophilic bacteria (AMC), Enterobacteriaceae (EB), Pseudomonadaceae (PS), lactic acid bacteria (LAB), yeast, moulds and presumptive Bacillus cereus were enumerated at the day of purchase and after storage at 4 °C for 7 or 12 days. Additionally, the presence of Salmonella spp. and Listeria monocytogenes was investigated. Isolates of presumptive spoilage bacteria were confirmed by partial 16S rRNA sequencing. At the day of purchase, 71.2% of the samples were of high microbiological quality and grouped into the low contamination category (AMC < 5.0 log cfu/g), while the sensory quality of 67.1% was categorized as “very good or good”. After storage, the number of samples with high microbial quality was 46.6%, and only 37.0% of the samples scored as “very good or good”. The most abundant species across all mushroom samples were the Pseudomonas fluorescens species complex (58.4%) and the potential mushroom pathogen Ewingella americana (28.3%). All mushroom samples tested negative for Salmonella spp., L. monocytogenes and Bacillus cereus. The microbiological and sensory quality of the analysed mushrooms at the day of purchase and after storage was considered to be good overall. Longer transport distances were found to have a significant influence on the microbiological and sensory quality.

Draft Genome Sequences of Three Pseudomonas fluorescens Strains Isolated from Marine Sponges Harvested off the West Coast of Ireland

Three Pseudomonas sp. strains isolated from marine sponges have shown potential quorum sensing inhibition (QSI) activity. We sequenced the draft genomes of the three strains with the goal of determining which genes or gene cluster(s) could be potentially involved in the QSI activity. Average nucleotide identity (ANI) and phylogenetic analysis classified the three strains as belonging to the Pseudomonas fluorescens species.

Colonization by multi-potential Pseudomonas aeruginosa P4 stimulates peanut (Arachis hypogaea L.) growth, defence physiology and root system functioning to benefit the root-rhizobacterial interface

The beneficial associations between Arachis hypogaea L. (peanut) and fluorescent Pseudomonas species have been poorly explored despite their predominance in the peanut rhizosphere. The present study explores the mutually beneficial interactions between peanut roots and P. aeruginosa P4 (P4) in terms of their impact on plant growth, defence physiology and the root-rhizobacterial interface. The efficient phosphate solubilizer P4 exhibited biocontrol abilities, including the production of siderophores, pyocyanin, indole-3-acetic acid and hydrogen cyanide. The bacterization of peanut seeds with multi-potential P4 significantly enhanced in vitro seed germination and seedling vigour. Under sand-based gnotobiotic (10 days post-inoculation) and sterile soil-based cultivation systems (30 days post-inoculation), sustained P4 colonization enhanced the peanut root length and dry plant biomass. The subsequent increase in catalase, polyphenol oxidase and phenylalanine ammonia lyase activities with increased phenolic contents in the peanut roots and shoots suggested the systemic priming of defences. Consequently, the altered root exudate composition caused enhanced chemo-attraction towards P4 itself and the symbiotic N2-fixing Bradyrhizobium strain. Co-inoculating peanuts with P4 and Bradyrhizobium confirmed the improved total bacterial colonization (∼2 fold) of the root tip, with the successful co-localization of both, as substantiated by scanning electron microscopy. Collectively, the peanut-P4 association could potentially model the beneficial Pseudomonas-driven multi-trophic rhizosphere benefits, emphasizing the plausible role of non-rhizobium PGPR in promoting N2 fixation.

Convergent gain and loss of genomic islands drive lifestyle changes in plant-associated Pseudomonas.

Host-associated bacteria can have both beneficial and detrimental effects on host health. While some of the molecular mechanisms that determine these outcomes are known, little is known about the evolutionary histories of pathogenic or mutualistic lifestyles. Using the model plant Arabidopsis, we found that closely related strains within the Pseudomonas fluorescens species complex promote plant growth and occasionally cause disease. To elucidate the genetic basis of the transition between commensalism and pathogenesis, we developed a computational pipeline and identified genomic islands that correlate with outcomes for plant health. One island containing genes for lipopeptide biosynthesis and quorum-sensing is required for pathogenesis. Conservation of the quorum-sensing machinery in this island allows pathogenic strains to eavesdrop on quorum signals in the environment and coordinate pathogenic behavior. We found that genomic loci associated with both pathogenic and commensal lifestyles were convergently gained and lost in multiple lineages through homologous recombination, possibly constituting an early step in the differentiation of pathogenic and commensal lifestyles. Collectively this work provides novel insights into the evolution of commensal and pathogenic lifestyles within a single clade of host-associated bacteria.

Isolation of Plant Growth Promoting fluorescent Pseudomonas from Mid-Himalayan Apple Orchards and their Similarity Analysis

Ten fluorescent Pseudomonas species isolated from normal and replant rhizosphere soil samples of apple collected from different locations of Shimla and Kullu districts of Himachal Pradesh. These Pseudomonas species solubilized tri calcium phosphate and showed substantial amount of soluble phosphorus in Pikovskay’s broth, exhibited the production of siderophore and growth inhibition against Dematophora necatrix, white root rot causing fungi in apple orchards. Random Amplified Polymorphic DNA analysis was done using four arbitary decamer primers of OPA series to observe genetic homogeneity/polymorphism among 10 isolates of fluorescent Pseudomonas species. Total 25 bands were generated with 4 random decamer oligonuceleotide primers. All the bands generated through RAPD-PCR were polymorphic in nature. The dendrogram constructed using UPGMA method showed that all the ten Pseudomonas isolates were categorized into three distinct clusters. The isolate An-9-Mg and An-H showed maximum similarity (67%) with each other and An-G showed 53% similarity with An-9-Mg and An-H. The isolate Ar-1-Mg was totally different from all other nine strains. Out of the ten Pseudomonas isolates, An-G and An-H showed maximum production of P-solubilization, siderophore and antifungal activity. Therefore, the uniqueness of Pseudomonas isolates An-G and An-H suggested their potential use for developing a cost effective and eco friendly biofertilizers for apple, an important cash crop of Himachal Pradesh.

Isolation of &amp;lt;i&amp;gt;Pseudomonas flurescens&amp;lt;/i&amp;gt; from Rhizosphere of Faba Bean and Screen Their Hydrogen Cyanide Production Under in Vitro Stduy, Ethiopia

Hydrogen cyanide is a highly toxic volatile compound which interferes with the cellular respiration by inhibiting the cytochrome oxidase enzyme in mitochondria. Root area of crops were consisting several bacteria that may have beneficial aspects. The objective of this study was to investigate the qualitative capability of hydrogen cyanide production by Pseudomonas fluorescens species isolates. Isolation of Pseudomonas fluorescens isolates were carried out on King’s B medium. Twelve Pseudomonas fluorescens species were isolated from the Rhizosphere of Fabaceae family namely faba bean screened for the production of hydrogen cyanide. For the production of hydrogen cyanide, Pseudomonas fluorescens isolates were streaked into King’s B agar plates supplemented with glycine. Total of Pseudomonas fluorescens isolates had a potential to produce hydrogen cyanide. Therefore, these isolated can be used as a biological control against plant pathogen microbes.

Isolation of &amp;lt;i&amp;gt;Pseudomonas fluorescens&amp;lt;/i&amp;gt; Species from faba Bean Rhizospheric Soil and Assessment of Indole Acetic Acid Production: In Vitro Study, Ethiopia

The microbial inoculants that are used in agriculture include phytohormone synthesis which have role to increase crop growth and yield products. Some microbes have a potential to synthesize plant hormone through utilize the root exudates of plant in rhizospheric area. The objective of this study was to isolate some Pseudomonas fluorescens species from rhizospheric soil of faba bean and tested their indole acetic acid production. Isolation of Pseudomonas fluorescens isolates were carried out on King’s B medium. All isolates Pseudomonas fluorescens were tseted for indole acetic acid production have a potential to produce phytohormone. The test Pseudomonas fluorescens isolates culture were inoculated in the nutrient broth with L-tryptophan 500 mg/l at 28 ± 2°C for one week. The results indicated that all most of the isolates tested possess plant growth promoting traits (phytohormone). So it could be concluded that all isolate Pseudomonas fluorescens can be used as plant growth promoting bacteria for synthesis of plant hormone resulting to increase of the plant growth and yield.

Antagonistic Effect of Pseudomonas sp. CMI-1 on Foodborne Pathogenic Listeria monocytogenes.

Bacterial isolates derived from food or raw food materials of animal origin were screened for potential antagonistic activity against foodborne pathogenic Listeria monocytogenes. Using the agar spot method, ten out of the 94 tested bacteria showed antilisterial activity. All of the antagonistic isolates identified by sequence analysis as strains of the genus Pseudomonas were able to inhibit the growth of all the examined Listeria species including the ruminal pathogenic L. ivanovii and the opportunistic human pathogenic L. innocua. Pseudomonas sp. CMI-1 had the highest inhibitory effect on the growth of different Listeria strains. Co-culturing studies revealed that the inhibition of L. monocytogenes could not be achieved efficiently. Although the population of the Pseudomonas sp. CMI-1 strain increased by up to 10 orders of magnitude during 2 days of culturing period at 20 °C in the presence of L. monocytogenes, the cell count of the pathogen also increased by approx. 6 orders of magnitude. At the same time, appropriate inhibition of cell-free supernatants generated from 6-day-old cultures of Pseudomonas sp. CMI-1 was observed. The inhibitory compound of this antagonistic strain is presumably a chromopeptide siderophore, whose activity and production can be affected by iron supplementation, and which had an absorption maximum typical of siderophores of fluorescent Pseudomonas species. Production of the antilisterial substance was influenced by the oxygen concentration, as in static cultures the concentration of the siderophore was higher than in shake flask cultures.

Microbiology, genomics, and clinical significance of the Pseudomonas fluorescens species complex, an unappreciated colonizer of humans.

Pseudomonas fluorescens is not generally considered a bacterial pathogen in humans; however, multiple culture-based and culture-independent studies have identified it at low levels in the indigenous microbiota of various body sites. With recent advances in comparative genomics, many isolates originally identified as the "species" P. fluorescens are now being reclassified as novel Pseudomonas species within the P. fluorescens "species complex." Although most widely studied for its role in the soil and the rhizosphere, P. fluorescens possesses a number of functional traits that provide it with the capability to grow and thrive in mammalian hosts. While significantly less virulent than P. aeruginosa, P. fluorescens can cause bacteremia in humans, with most reported cases being attributable either to transfusion of contaminated blood products or to use of contaminated equipment associated with intravenous infusions. Although not suspected of being an etiologic agent of pulmonary disease, there are a number of reports identifying it in respiratory samples. There is also an intriguing association between P. fluorescens and human disease, in that approximately 50% of Crohn's disease patients develop serum antibodies to P. fluorescens. Altogether, these reports are beginning to highlight a far more common, intriguing, and potentially complex association between humans and P. fluorescens during health and disease.

Occurrence of multi-antibiotic resistant Pseudomonas spp. in drinking water produced from karstic hydrosystems

Aquatic environments could play a role in the spread of antibiotic resistance genes by enabling antibiotic-resistant bacteria transferred through wastewater inputs to connect with autochthonous bacteria. Consequently, drinking water could be a potential pathway to humans and animals for antibiotic resistance genes. The aim of this study was to investigate occurrences of Escherichia coli and Pseudomonas spp. in drinking water produced from a karst, a vulnerable aquifer with frequent increases in water turbidity after rainfall events and run-offs. Water samples were collected throughout the system from the karstic springs to the drinking water tap during three non-turbid periods and two turbid events. E. coli densities in the springs were 10- to 1000-fold higher during the turbid events than during the non-turbid periods, indicating that, with increased turbidity, surface water had entered the karstic system and contaminated the spring water. However, no E. coli were isolated in the drinking water. In contrast, Pseudomonas spp. were isolated from the drinking water only during turbid events, while the densities in the springs were from 10- to 100-fold higher than in the non-turbid periods. All the 580 Pseudomonas spp. isolates obtained from the sampling periods were resistant (to between 1 and 10 antibiotics), with similar resistance patterns. Among all the Pseudomonas isolated throughout the drinking water production system, between 32% and 86% carried the major resistance pattern: ticarcillin, ticarcillin–clavulanic acid, cefsulodin, and/or aztreonam, and/or sulfamethoxazol–trimethoprim, and/or fosfomycin. Finally, 8 Pseudomonas spp. isolates, related to the Pseudomonas putida and Pseudomonas fluorescens species, were isolated from the drinking water. Thus, Pseudomonas could be involved in the dissemination of antibiotic resistance via drinking water during critical periods.

Genetic and functional diversity of fluorescent Pseudomonas from rhizospheric soils of wheat crop

Wheat rhizospheric soils were collected from different part of northern and eastern Indo-Gangetic plains, which is being irrigated from water of Ganga River. Isolation of fluorescent Pseudomonas species was carried out from the soil samples collected. The percentage of isolates positive for indolic compound, P-solubilisation, siderophore production and ACC deaminase activity were 64.0, 38.6, 63.5, and 19.7, respectively. A total of 543 isolates were randomly selected for studies based on the genus specific confirmation by the Pseudomonas specific primer. Among the 543 isolates, 26 different clusters were formed from 16S rDNA-RFLP whereas 27 clusters were generated by the rpoB-RFLP with similarity percent ranging from 3 to 100%. 16S rDNA sequencing showed 9 different species of Pseudomonas whereas, rpoB sequencing showed 13 different species of Pseudomonas. Phylogenetic analysis based on 16S rDNA gene sequences generated 15 branches showing the more than 70% of boot strap value, whereas 18 branches in the rpoB based phylogenetic tree were supported by bootstrap values above 70%. Diversity indices based on rpoB were higher than the ribosomal RNA gene.

Uranium (VI) Complexation with Siderophores-pyoverdine Produced by Pseudomonas Fluorescens SHA 281

Fluore sce nt Pseudomonas species produce pyove rdine -type siderophores with a high pote ntial to dissolve ; bind and transport uranium in the e nvironment. Ide ntification of Pseudomonas fluorescens SHA 281 was confirme d by 16S rDNA sequ e ncing. The pyoverdine produce d by the tested strain was e xtracte d and purifie d using XAD-4 Ambe rlite re sin and its chemical structure was confirme d using NMR and CA-MS analyses. The ge l e lectrophoresis of pyoverdine appeare d low molecular we ight with one prote in band at ~12.5 kDa. The ge ne responsible for pyoverdine production was ide ntifie d using PCR technique . Unde r optimum conditions for comple xation, it was found that pyoverdine comple xe d with about 90.48 % and 86.41 % of U (VI) from monazite and (Th-U) concen trate, respectively.

Evolution of REP diversity: a comparative study

BackgroundRepetitive extragenic palindromic elements (REPs) constitute a group of bacterial genomic repeats known for their high abundance and several roles in host cells´ physiology. We analyzed the phylogenetic distribution of particular REP classes in genomic sequences of sixty-three bacterial strains belonging to the Pseudomonas fluorescens species complex and ten strains of Stenotrophomonas sp., in order to assess intraspecific REP diversity and to gain insight into long-term REP evolution.ResultsBased on proximity to RAYT (REP-associated tyrosine transposase) genes, twenty-two and thirteen unique REP classes were determined in fluorescent pseudomonads and stenotrophomonads, respectively. In stenotrophomonads, REP elements were typically found in tens or a few hundred copies per genome. REPs of fluorescent pseudomonads were generally more numerous, occurring in hundreds or even over a thousand perfect copies of particular REP class per genome. REP sequences showed highly heterogeneous distribution. The abundances of REP classes roughly followed host strains´ phylogeny, differing markedly among individual clades. High abundances of particular REP classes appeared to depend on the presence of the cognate RAYT gene, and deviations from this state could be attributed to recent or ancient mutations of rayt-flanking REPs, or RAYT loss. RAYTs of both studied bacterial groups are monophyletic, and their cognate REPs show species-specific characteristics, suggesting shared evolutionary history of REPs, RAYTs and their hosts.ConclusionsThe results of our large-scale analysis show that REP elements constitute intriguingly dynamic components of genomes of fluorescent pseudomonads and stenotrophomonads, and indicate that REP diversification and proliferation are ongoing processes. High numbers of REPs have apparently been retained during the entire evolutionary time since the establishment of these two bacterial lineages, probably because of their beneficial effect on host long-term fitness. REP elements in these bacteria represent a suitable platform to study the interplay between repeated elements, their mobilizers and host bacterial cells.

Determination of the sensitivity of bacteria to barium ions, a taxonomic marker of the genus Pseudomonas

Comparative efficacy of the determination of the sensitivity of bacterial cells to barium ions was evaluated on a synthetic nutrient medium, FMH agar, Mueller-Hinton agar, and AGV agar. The synthetic nutrient medium developed for this study contained L-proline and L-glutamine as the sole nitrogen and carbon source, which promoted growth of all Pseudomonas strains and ensured the minimal level of barium binding. The sensitivity of 80 strains belonging to 11 Pseudomonas species, including the type strains, as well as of 80 strains of 22 other bacterial species, was studied. The sensitivity of bacteria to barium ions was determined by using serial dilutions of barium chloride in the nutrient medium. The highest level of analytical sensitivity of pseudomonads to barium ions was determined on the synthetic nutrient medium: the minimal inhibitory concentration (MIC) values of barium chloride ranged from 0.5 to 6 g/L, the MIC90 value was 2 g/L. At the same time, 86.1% of all strains of fluorescent Pseudomonas species produced fluorescein on the control BaCl2-free synthetic nutrient medium. For representatives of other genera grown on all the studied nutrient media, the MIC values of barium chloride ranged from 20 to 50 g/L. The proposed method for determination of the sensitivity of bacteria to barium ions using the synthetic nutrient medium with 6 g/L of barium chloride as a criterion for the classification of barium-sensitive strains to the genus Pseudomonas is suitable for standardization.

Eco-benign enzymatic dehairing of goatskins utilizing a protease from a Pseudomonas fluorescens species isolated from fish visceral waste

The dehairing of skin/hide is the most polluting process of all leather manufacturing processes. In this study, an attempt has been made to extract a crude bacterial protease from fish visceral wastes and to utilize the protease to dehair goatskins. The bacterial species isolated has been identified by biochemical tests and microscopic examination as Pseudomonas fluorescens. The optimum pH and temperature conditions for the maximal activity of the extracted crude protease have been determined to be 10.5 and 40 °C, respectively. It has been found that a combination of the extracted crude protease with a small amount of sodium sulfide allows for the complete dehairing of goatskins without the use of lime. The enzyme-dehaired goat leathers were evaluated by mechanical, touch–visual and by electron microscopy and were compared to conventionally dehaired goat leathers. The results indicate that the enzyme-dehaired leathers exhibit similar or improved characteristics. In essence, this report provides a do-only, eco-friendly approach to cleaner leather processing by utilizing natural resources derived from fish-industry biowastes, which may reduce the leather industry’s generation of toxic chemical wastes.