Microbiome analyses of 12 psyllid species of the family Psyllidae identified various bacteria including Fukatsuia and Serratia symbiotica, known as secondary symbionts of aphids.

BACKGROUND: Psyllids (Hemiptera: Psylloidea) comprise a group of plant sap-sucking insects that includes important agricultural pests. They have close associations not only with plant pathogens, but also with various microbes, including obligate mutualists and facultative symbionts. Recent studies are revealing that interactions among such bacterial populations are important for psyllid biology and host plant pathology. In the present study, to obtain further insight into the ecological and evolutionary behaviors of bacteria in Psylloidea, we analyzed the microbiomes of 12 psyllid species belonging to the family Psyllidae (11 from Psyllinae and one from Macrocorsinae), using high-throughput amplicon sequencing of the 16S rRNA gene. RESULTS: The analysis showed that all 12 psyllids have the primary symbiont, Candidatus Carsonella ruddii (Gammaproteobacteria: Oceanospirillales), and at least one secondary symbiont. The majority of the secondary symbionts were gammaproteobacteria, especially those of the family Enterobacteriaceae (order: Enterobacteriales). Among them, symbionts belonging to "endosymbionts3", which is a genus-level monophyletic group assigned by the SILVA rRNA database, were the most prevalent and were found in 9 of 11 Psyllinae species. Ca. Fukatsuia symbiotica and Serratia symbiotica, which were recognized only as secondary symbionts of aphids, were also identified. In addition to other Enterobacteriaceae bacteria, including Arsenophonus, Sodalis, and "endosymbionts2", which is another genus-level clade, Pseudomonas (Pseudomonadales: Pseudomonadaceae) and Diplorickettsia (Diplorickettsiales: Diplorickettsiaceae) were identified. Regarding Alphaproteobacteria, the potential plant pathogen Ca. Liberibacter europaeus (Rhizobiales: Rhizobiaceae) was detected for the first time in Anomoneura mori (Psyllinae), a mulberry pest. Wolbachia (Rickettsiales: Anaplasmataceae) and Rickettsia (Rickettsiales: Rickettsiaceae), plausible host reproduction manipulators that are potential tools to control pest insects, were also detected. CONCLUSIONS: The present study identified various bacterial symbionts including previously unexpected lineages in psyllids, suggesting considerable interspecific transfer of arthropod symbionts. The findings provide deeper insights into the evolution of interactions among insects, bacteria, and plants, which may be exploited to facilitate the control of pest psyllids in the future.

A natural symbiotic bacterium drives mosquito refractoriness to Plasmodium infection via secretion of an antimalarial lipase.

The stalling global progress in the fight against malaria prompts the urgent need to develop new intervention strategies. Whilst engineered symbiotic bacteria have been shown to confer mosquito resistance to parasite infection, a major challenge for field implementation is to address regulatory concerns. Here, we report the identification of a Plasmodium-blocking symbiotic bacterium, Serratia ureilytica Su_YN1, isolated from the midgut of wild Anopheles sinensis in China that inhibits malaria parasites via secretion of an antimalarial lipase. Analysis of Plasmodium vivax epidemic data indicates that local malaria cases in Tengchong (Yunnan province, China) are significantly lower than imported cases and importantly, that the local vector A. sinensis is more resistant to infection by P. vivax than A. sinensis from other regions. Analysis of the gut symbiotic bacteria of mosquitoes from Yunnan province led to the identification of S. ureilytica Su_YN1. This bacterium renders mosquitoes resistant to infection by the human parasite Plasmodium falciparum or the rodent parasite Plasmodium berghei via secretion of a lipase that selectively kills parasites at various stages. Importantly, Su_YN1 rapidly disseminates through mosquito populations by vertical and horizontal transmission, providing a potential tool for blocking malaria transmission in the field.

Serratia rhizosphaerae sp. nov., a novel plant resistance inducer against soft rot disease in tobacco.

A novel Gram-negative, facultatively anaerobic, non-spore-forming and rod-shaped bacterial strain (KUDC3025T) was isolated from rhizospheric soil of Artemisia japonica subsp. littoricola collected from the Dokdo Islands, Republic of Korea and bacterial strain MYb239 was isolated from compost from Kiel, Germany. Phylogenetic analysis based on 16S rRNA gene sequences, multilocus genes (atpD, gyrB, infB and rpoB), and whole-genome sequences indicated that both strains belonged to the genus Serratia and were most closely related to Serratia rubidaea KCTC 2927T. The average nucleotide identity values based on blast and MUMmer, tetranucleotide usage pattern and genome-based digital DNA-DNA hybridization values were all below the 95.0 %/95.0 %/0.998/70 % cutoff points. The genome G+C content was 58.0 mol%. The cellular quinone content contained ubiquinone-8 and the major components in the fatty acid profile were C16 : 0, C17 : 0 cyclo and C14 : 0. The polar lipid profile included diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, four unknown amino lipids, two unknown phospholipids and an unknown lipid. Based on phenotypic, chemotaxonomic and genotypic data, strain KUDC3025T (DSM 106578T=CGMCC 1.18473T) and MYb239 represents a novel species, for which the name Serratia rhizosphaerae sp. nov. is proposed. Furthermore, strain KUDC3025T was able to suppress disease symptoms by priming the plant defence system components, including the salicylic acid and ethylene pathways, furthering our understanding of Serratia as potential plant growth promoting bacteria.

Diversity of Culturable Bacteria Isolated From the Feces of Wild Anopheles darlingi (Diptera: Culicidae) Mosquitoes From the Brazilian Amazon.

Microorganisms living in the midgut of Anopheles mosquitoes have been studied to fight vector-borne diseases, such as malaria. Studies on the microbiota of the Neotropical Anopheles darlingi, the most important Brazilian vector for malaria, have been reported for the same purpose. Our aims were to isolate and identify culturable bacteria from An. darlingi mosquito guts through their feces and to estimate the species richness and the frequency distribution of the sampled bacteria. Sixty wild females of An. darlingi mosquitoes were captured at two rural locations, near Porto Velho, Rondônia, Brazil. Bacteria were isolated from mosquito feces, which were collected using cages which permit the collection of feces on LB nutrient agar plates. Sixty bacterial colonies were isolated and stored in glycerol at -80°C. Bacteria were identified by sequencing their 16S rRNA gene obtained using PCR and Sanger sequencing. To aid in species identification, MALDI-TOF, VITEK2, and BBL Crystal were used as complementary protocols. The sequences obtained from the 60 bacterial isolates were compared to sequences deposited in GenBank (NCBI) using BLAST. Homology greater than 97% between the query and the subject was used as the criteria for assigning the identity of each isolate. Fourteen species from eight different genera were identified among the 60 isolates. The most frequent species were Serratia liquefaciens (20%) and Serratia marcescens (15%). Due to their established apathogenicity and according to previous studies, we suggest Serratia and Pantoea species as suitable for paratransgenesis development to fight malaria in Brazilian Amazon.

Serratia Chorioamnionitis and Culture Proven Sepsis in a Preterm Neonate: A Case Report and Review of the Literature.

BACKGROUND: Serratia marcescens is a well-known cause of nosocomial infectious outbreaks in the neonatal intensive care unit, with a high mortality rate in the vulnerable preterm population. However, it is not typically associated with neonatal sepsis secondary to intrapartum vertical transmission. We present the case of a preterm male born at 25 weeks and 4 days of gestation in Okinawa, Japan with culture-proven S. marcescens chorioamnionitis and sepsis, as well as a review of the previously published literature. METHODS: We conducted a literature search utilizing MeSH indexing with the headings [chorioamnionitis], [Serratia], and [infant, newborn] limited to "humans" with a publication date range between 1950 and 2020. RESULTS: All reported cases of preterm S. marcescens chorioamnionitis occurred in coastal locations. The majority of cases resulted in spontaneous abortion, and we found no published reports of confirmed S. marcescens chorioamnionitis in conjunction with viable preterm delivery and positive neonatal cultures. In the case presented herein, S. marcescens chorioamnionitis with associated neonatal sepsis was confirmed by positive placental and blood cultures. Bacterial clearance was achieved following an antibiotic course consisting of 5 days of gentamicin and 14 days of meropenem therapy. CONCLUSIONS: S. marcescens is an uncommon cause of chorioamnionitis that can have devastating neonatal consequences, especially in the at-risk preterm population.

Isolation of Serratia fonticola Producing FONA, a Minor Extended-Spectrum ß-Lactamase (ESBL), from Imported Chicken Meat in Japan.

Five novel strains of Serratia fonticola that produce FONA, a minor extended-spectrum beta-lactamase (ESBL), were isolated during routine surveillance of ESBL-producing Enterobacteriaceae in imported chicken meat in Japan in 2017 and 2018. These strains exhibited a clear ESBL phenotype in susceptibility tests carried out in the presence of clavulanic acid; however, all strains tested negative in a multiplex polymerase chain reaction assay used to detect TEM, SHV, and CTX-M ß-lactamase genes. After identification of the bacterial species as S. fonticola, full length blaFONA genes were amplified and the DNA sequences were determined. The blaFONA genes from all 5 strains were different from those previously reported (blaFONA-1 to blaFONA-6); they clustered close to one another but were distinct from previously reported blaFONA genes in a phylogenic analysis based on amino acid sequences.

Exit site infection and peritonitis due to Serratia species in patients receiving peritoneal dialysis: Epidemiology and clinical outcomes.

AIM: To study the epidemiology and clinical outcomes of catheter-related infections of Serratia species in peritoneal dialysis (PD) patients. METHODS: We retrospectively reviewed the patient characteristics, antibiotics susceptibility/resistance patterns and treatment outcomes of exit site infection (ESI) and peritonitis due to Serratia in PD patients during the period of 2004 to 2017. RESULTS: One hundred and sixty-one patients had Serratia ESI, of which 10 (6.2%) progressed to tunnel tract involvement and 11 (6.8%) developed PD peritonitis. Nineteen (11.8%) patients with Serratia ESI failed to respond to medical treatment and required catheter removal. Fifty-six (34.8%) patients had repeat Serratia ESI, which occurred at 12.9 ± 13.6 months after the previous episode. Twenty-two patients had Serratia peritonitis, which accounted for 1% of peritonitis during the study period. Ten (45.5%) patients responded to medical treatment while 12 (54.5%) patients required catheter removal. Nine patients (36.4%) failed to resume PD and were converted to long-term haemodialysis. Two patients had repeat peritonitis at 2 months and 3 years, respectively, after the initial episode. Serratia species in PD patients showed high rates of resistance to ampicillin, and first- and second-generation cephalosporins, but were generally susceptible to aminoglycosides, carboxy-/ureido-penicillins and carbapenems. CONCLUSION: Our results suggest that Serratia ESI show low risk of progression to peritonitis and favourable response to medical therapy, while Serratia peritonitis was associated with high rates of catheter removal and peritoneal failure.

Serratia inhibens sp. nov., a new antifungal species isolated from potato (Solanum tuberosum).

A novel bacterial strain, S40T, with strong antifungal activity was isolated from the rhizosphere of green potato collected from Zealand, Denmark. Polyphasic analysis with a combined phenotypic, phylogenetic and genomic approach was used to characterize S40T. Phylogenetic analysis based on the 16S rRNA gene and MLSA (concatenated gyrB, rpoD, infB and atpD sequences) showed that strain S40T was affiliated with the genus Serratia and with Serratia plymuthica PRI-2C as the closest related strain [average nucleotide identity (ANI), 99.26 %; DNA-DNA hybridization (dDDH), 99.20%]. However, whole genome sequence analyses revealed that S40T and S. plymuthica PRI-2C genomes displayed lower similarities when compared to all other S. plymuthica strains (ANI ≤94.34 %; dDDH ≤57.6 % relatedness). The DNA G+C content of strain S40T was determined to be 55.9 mol%. Cells of the strain were Gram-negative, rod-shaped, facultative anaerobic and displayed growth at 10-37 °C (optimum, 25-30 °C) and at pH 6-9 (optimum, pH 6-7). Major fatty acids were C16 : 0 (27.9 %), summed feature (C16 : 1 ω6c/C16 : 1 ω7c; 18.0 %) and C17 : 0 cyclo (15.1 %). The respiratory quinone was determined to be Q8 (94 %) and MK8 (95 %) and the major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The results of phenotypic, phylogenetic and genomic analyses support the hypothesis that strain S40T represents a novel species of the genus Serratia, for which the name Serratia inhibens sp. nov. is proposed. The type strain is S40T (=LMG 31467T=NCIMB 15235T). In addition, we propose that S. plymuthica PRI-2C is reclassified and transferred to the species S. inhibens as S. inhibens PRI-2C.

Serratia nevei sp. nov. and Serratia bockelmannii sp. nov., isolated from fresh produce in Germany and reclassification of Serratia marcescens subsp. sakuensis Ajithkumar et al. 2003 as a later heterotypic synonym of Serratia marcescens subsp. marcescens.

Fifteen enterobacterial strains were isolated from fresh produce. The 16S rRNA gene sequences indicated that these belong to Serratia, with twelve strains showing 99.57%-99.93% and three strains showing 99.86-100% 16S rRNA gene sequence similarity with Serratia marcescens and Serratia nematodiphila as nearest neighbors, respectively. Further comparative multi locus sequence analyses, as well as phylogenomic comparisons, revealed that 6 of the 15 strains were well-separated from their nearest neighbors and formed two clearly distinct taxa. Strains S2, S9, S10 and S15T were urease-positive, while strains S3T and S13 were urease-negative. Average nucleotide identity and digital DNA-DNA hybridization comparisons of representative strains S3T and S15T with type strains of S. marcescens, S. nematodiphila and S. ureilytica indicated that these shared less than 96% and 70% homology, respectively. Major fatty acids of strains S3T and S15T included C16:0, C16:1 ω7c/C16:1 ω6c, C17:0 Cyclo and C18:1 ω6c /C18:1 ω7c. The mol% G+C of genomic DNA of strain S15T was 59.49% and of strain S3T was 59.04. These results support the description of two novel species, Serratia nevei and Serratia bockelmannii, with strains S15T (=LMG 31536T =DSM 110085T) and S3T (=LMG 31535T =DSM 110152T) as type strains, respectively. Although Serratia marcescens subsp. sakuensis was previously described to form spores, spores could not be determined in this study. As spore formation was the only differential characteristic of this subspecies, S. marcescens subsp. sakuensis is a later heterotypic synonym of Serratia marcescens.

Serratia Liver Abscess Infection and Cardiomyopathy in a Patient with Diabetes Mellitus: A Case Report and Review of the Literature.

BACKGROUND Liver abscesses remain difficult to diagnose and treat. Risk factors include diabetes mellitus, liver cirrhosis, and immunodeficiency. The majority are pyogenic, resulting from bacterial infection. Research identifies species in the Serratia genus as the cause of pyogenic liver abscesses in only 0.25% of cases and only 1 Serratia species in each case appears to have been identified. To the best of our knowledge, the present case report is the first to involve overlapping Serratia species in a single liver abscess infection that induced cardiomyopathy. CASE REPORT A 45-year-old woman presented to our Emergency Department (ED) for severe generalized weakness. Initial test results indicated a diagnosis of microcytic anemia, hypomagnesemia, hypokalemia, hypocalcemia, hyperglycemia, type 2 diabetes mellitus, and severe heart failure. A computed tomography scan showed a 10-cm rim-enhancing fluid collection in the right hepatic lobe. Fluid drained from the suspected abscess tested positive for Serratia marcescens and Streptococcus viridans. The patient was treated with ceftriaxone and metronidazole, which she tolerated well. The abscess decreased to less than 9.8 mm. Twenty-one weeks after discharge, the patient received a cholecystectomy. Fluid drained from the residual abscess cultured positive for a different Serratia species, S. odorifera. CONCLUSIONS Diabetes mellitus and acute cholecystitis were key factors in the initial infections and abscess. We also suspect this is a rare case of cardiomyopathy induced by a Serratia infection. The source of the Serratia odorifera is less certain, as it postdates placement of a percutaneous drain, raising the potential for a nosocomial infection but not precluding the possibility that both Serratia species were previously present.

The application of selected ion flow tube-mass spectrometry to follow volatile formation in modified-atmosphere-packaged cooked ham.

Cooked pork products, i.e., sliced cooked hams maintained under modified-atmosphere-packaging (MAP), were analysed both microbiologically and with respect to volatile levels during storage. Three storage temperature ranges were compared (4-6 °C, 7-9 °C, and 11-13 °C), representing different refrigeration conditions at household level. The microbial loads were determined by plating samples on six different agar media, followed by (GTG)5-PCR fingerprinting of genomic DNA of selected isolates, and identification of representative isolates by 16S rRNA, pheS, and rpoA gene sequencing. Carnobacterium maltaromaticum, Lactobacillus sakei, and Serratia proteamaculans were the major bacterial species found among the 619 isolates identified. The volatiles produced during storage were followed by selected ion flow tube-mass spectrometry (SIFT-MS) and the identity of the volatiles was confirmed by headspace solid-phase microextraction combined with gas chromatography and time-of-flight mass spectrometry (HS-SPME-GC-TOF-MS). SIFT-MS analysis showed that volatiles, such as 2,3-butanediol, acetoin, and ethanol, may serve as potential markers for spoilage development. Differences in volatile production between samples were likely due to discrepancies in the initial microbial load and the effect of storage conditions. In conclusion, this study combines the use of new mass spectrometric techniques to examine volatile production during spoilage as an additional source of information during microbiological community analysis.

The nematicide Serratia plymuthica M24T3 colonizes Arabidopsis thaliana, stimulates plant growth, and presents plant beneficial potential.

Nine bacterial strains were previously isolated in association with pinewood nematode (PWN) from wilted pine trees. They proved to be nematicidal in vitro, and one of the highest activities, with potential to control PWN, was showed by Serratia sp. M24T3. Its ecology in association with plants remains unclear. This study aimed to evaluate the ability of strain M24T3 to colonize the internal tissues of the model plant Arabidopsis thaliana using confocal microscopy. Plant growth-promoting bacteria (PGPB) functional traits were tested and retrieved in the genome of strain M24T3. In greenhouse conditions, the bacterial effects of all nematicidal strains were also evaluated, co-inoculated or not with Bradyrhizobium sp. 3267, on Vigna unguiculata fitness. Inoculation of strain M24T3 increased the number of A. thaliana lateral roots and the confocal analysis confirmed effective bacterial colonization in the plant. Strain M24T3 showed cellulolytic activity, siderophores production, phosphate and zinc solubilization ability, and indole acetic acid production independent of supplementation with L-tryptophan. In the genome of strain M24T3, genes involved in the interaction with the plants such as 1-aminocyclopropane-1-carboxylate (ACC) deaminase, chitinolytic activity, and quorum sensing were also detected. The genomic organization showed ACC deaminase and its leucine-responsive transcriptional regulator, and the activity of ACC deaminase was 594.6 nmol α-ketobutyrate µg protein-1 µl-1. Strain M24T3 in co-inoculation with Bradyrhizobium sp. 3267 promoted the growth of V. unguiculata. In conclusion, this study demonstrated the ability of strain M24T3 to colonize other plants besides pine trees as an endophyte and displays PGPB traits that probably increased plant tolerance to stresses.

Serratia microhaemolytica sp. nov., isolated from an artificial lake in Southern China.

A Gram-stain negative, facultatively anaerobic, rod-shaped, non-motile and non-spore forming bacterium, designated ZS-11T, was isolated from an artificial freshwater lake in Guangzhou city, Guangdong province, China. Growth of strain ZS-11T was observed at the temperature 18-42 °C (optimum 32-37 °C), pH 6.0-8.0 (optimum 7.0) and 0.5-3.0% (w/v) NaCl (optimum 0.5%, w/v), and also found to be enhanced in the presence of CO2. Pairwise comparison of 16S rRNA gene sequences showed that the strain shared high similarities with Serratia entomophila DSM 12358T (96.1%), Serratia ficaria DSM 4569T (96.0%), Serratia plymuthica DSM 4540T (96.0%), Rahnella victoriana FRB 225T (95.9%) and Rouxiella badensis DSM 100043T (95.8%). The phylogenomic dendrograms showed that strain ZS-11T formed a distinct cluster within the clade of the genus Serratia. The major fatty acids (> 20%) present in the cells were C16:0, C16:1ω7c/C16:1ω6c and C18:1ω7c/C18:1ω6c, which were consistent with those of S. entomophila CCUG 55496T and Serratia liquefaciens CCUG 9285T. The DNA G + C content for the genome was 49.3%. Based on these phenotypic and genotypic data, strain ZS-11T is considered to represent a new species of the genus Serratia, for which the name Serratia microhaemolytica sp. nov. is proposed. The type strain is ZS-11T (= CCTCC AB 2018040T = KCTC 62413T).

The Microbiome of the Maculinea-Myrmica Host-Parasite Interaction.

Maculinea (=Phengaris) are endangered butterflies that are characterized by a very complex biological cycle. Maculinea larvae behave as obligate parasites whose survival is strictly dependent on both particular food plants and species-specific Myrmica ants. In this interaction, Maculinea caterpillars induce Myrmica workers to retrieve and rear them in the nest by chemical and acoustic deception. Social insect symbiotic microorganisms play a key role in intraspecific and interspecific communication; therefore, it is possible that the Maculinea caterpillar microbiome might be involved in the chemical cross-talk by producing deceptive semiochemicals for host ants. To address this point, the microbiota of Maculinea alcon at different larval stages (phytophagous early larvae, intermediate larvae, carnivorous late larvae) was analyzed by using 16S rRNA-guided metabarcoding approach and compared to that of the host ant Myrmica scabrinodis. Structural and deduced functional profiles of the microbial communities were recorded, which were used to identify specific groups of microorganisms that may be involved in the chemical cross-talk. One of the most notable features was the presence in all larval stages and in the ants of two bacteria, Serratia marcescens and S. entomophila, which are involved in the chemical cross-talk between the microbes and their hosts.

Characterization of Bacterial Microbiota in Tilapia Fillets Under Different Storage Temperatures.

This paper investigates the bacterial microbiota in tilapia fillets under cold (4 °C), iced (0 °C), and superchilled (-3 °C) storage conditions. At 4 °C, at least seven species/strains of Pseudomonas were detected in the fillets, five of which were dominant either at a certain stage or throughout the entire storage period. Shewanella was less dominant than Pseudomonas at 4 °C, while Serratia became dominant after 6 days storage at 4 °C. The microbiota in fillets stored at 0 and -3 °C were very similar and rarely changed during storage, yet differed greatly from the microbiota at 4 °C. Only two Pseudomonas species/strains grew at 0 and -3 °C, one of which was the most dominant. A Vibrionimonas sp. not found at 4 °C was found to be the second most dominant species at 0 and -3 °C. Shewanella and Psychrobacter were also present at 0 and -3 °C but were the minor genera. The most dominant strains at -3, 0, and 4 °C were separately isolated and subjected to full length 16S rDNA sequencing, which demonstrated that they were identical and were Pseudomonas fluorescens. The changes of the total bacterial count and TVBN value of the fillets inoculated with the isolated P. fluorescens were very similar to those of fillets with natural microbiota. This implies that P. fluorescens is the most important spoiler of tilapia fillets at -3, 0, or 4 °C. PRACTICAL APPLICATION: This research shows that fewer species of bacteria survive at 0 and -3 °C than those at 4 °C, while among these bacteria, the most important spoiler is P. fluorescens. This may provide some clues to extend the shelf life of tilapia fillets by taking some inhibitory measures targeted at P. fluorescens in the future.

Environmental potassium regulates bacterial flotation, antibiotic production and turgor pressure in Serratia through the TrkH transporter.

Serratia sp. strain ATCC 39006 (S39006) can float in aqueous environments due to natural production of gas vesicles (GVs). Expression of genes for GV morphogenesis is stimulated in low oxygen conditions, thereby enabling migration to the air-liquid interface. Quorum sensing (via SmaI and SmaR) and transcriptional and post-transcriptional regulators, including RbsR and RsmA, respectively, connect the control of cell buoyancy, motility and secondary metabolism. Here, we define a new pleiotropic regulator found in screens of GV mutants. A mutation in the gene trkH, encoding a potassium transporter, caused upregulation of GV formation, flotation, and the prodigiosin antibiotic, and downregulation of flagellar motility. Pressure nephelometry revealed that the mutation in trkH affected cell turgor pressure. Our results show that osmotic change is an important physiological parameter modulating cell buoyancy and antimicrobial production in S39006, in response to environmental potassium levels.

Endophytic bacteria isolated from Solanum nigrum L., alleviate cadmium (Cd) stress response by their antioxidant potentials, including SOD synthesis by sodA gene.

Cadmium (Cd) is a toxic heavy metal and an abiotic stressor to plants; however, inoculation of endophytic bacteria can raise resistance in plants against Cd, as well as improve plant growth. In the present study, two endophytic bacterial strains were isolated from Solanum nigrum, identified as Serratia sp. IU01 and Enterobacter sp. IU02 by 16S DNA sequencing. Both IU01 and IU02 were tolerant up to 9.0 mM of Cd in culture broth and successive increase in Cd concentration from 0 mM to 9.0 mM, led to an increase in the SOD enzyme activity of the isolates. Both strains were capable of indole-3-acetic acid (IAA) synthesis and phosphate solubilization, detected through gas spectrometry-mass chromatography (GC-MS) and Pikovskaya agar medium respectively. Brassica juncea plants stressed with 0-25 mg/kg Cd showed retardation in all growth attributes, however, inoculation of strain IU01 and IU02 significantly promoted the plant growth attributes as compared to control. Moreover, antioxidant enzymes and metabolites against reactive oxygen species (ROS) including polyphenol oxidase (PPO), peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), alcohol dehydrogenase (ADH), reduced glutathione (GSH), malondialdehyde (MDA), flavonoid and polyphenolic contents were also significantly relieved by inoculation of IU01 and IU02 in plant exposed to different concentration of Cd stress as compared to control plants. Phytohormone production, phosphate solubilization, and/or antioxidative support of IU01 and IU02 might be responsible for growth promotion and Cd resistance in the plant.

Isolation and characterization of endophytes from nodules of Mimosa pudica with biotechnological potential.

Legumes establish symbiotic relationships with different microorganisms, which could function as plant growth promotion microorganisms (PGPM). The finding of new PGPM strains is important to increase plant production avoiding or diminishing the use of industrial fertilizers. Thus, in this work we evaluated the plant growth promotion traits of ten strains isolated from Mimosa pudica root nodules. According to the 16S rDNA sequence, the microorganisms were identified as Enterobacter sp. and Serratia sp. To the best of our knowledge this is the first report describing and endophytic interaction between Mimosa pudica and Enterobacter sp. These strains have some plant growth promoting traits such as phosphate solubilization, auxin production and cellulase and chitinase activity. Strains identified as Serratia sp. inhibited the growth of the phytopathogenic fungi Fusarium sp., and Alternaria solani and the oomycete Phytophthora capsici. According to their biochemical characteristics, three strains were selected to test their plant growth promoting activity in a medium with an insoluble phosphate source. These bacteria show low specificity for their hosts as endophytes, since they were able to colonize two very different legumes: Phaseolus vulgaris and M. pudica. Seedlings of P. vulgaris were inoculated and grown for fifteen days. Enterobacter sp. NOD1 and NOD10, promoted growth as reflected by an increase in shoot height as well as an increase in the size and emergence of the first two trifolia. We could localize NOD5 as an endophyte in roots in P. vulgaris by transforming the strain with a Green Fluorescent Protein carrying plasmid. Experiments of co-inoculation with different Rhizobium etli strains allowed us to discard that NOD5 can fix nitrogen in the nodules formed by a R. etli Fix- strain. The isolates described in this work show biotechnological potential for plant growth promoting activity and production of indoleacetic acid and siderophores.

Purification and characterization of the thermostable protease produced by Serratia grimesii isolated from channel catfish.

BACKGROUND: Microbial spoilage of fishery products accounts for significant financial losses, yearly on a global scale. Psychrotrophic spoilage bacteria often secrete extracellular enzymes to break down surrounding fish tissue, rendering the product unsuitable for human consumption. For a better understanding of bacterial spoilage due to enzymatic digestion of fish products, proteases in Serratia grimesii isolated from North American catfish fillets (Ictalurus punctatus) were investigated. RESULTS: Mass spectrometric evidence demonstrated that S. grimesii secretes two distinct extracellular proteases and one lipase. Protease secretion displayed broad thermostability in the 30-90 °C range. The major protease-secretion (O-1) was most active under alkaline conditions and utilized manganese as a co-factor. Organic solvents significantly disrupted the efficacy of S. grimesii extracellular enzymes and, in a series of bactericidal detergents, protease activity was highest when treated with Triton X-100. Ethylenediaminetetraacetic acid (EDTA) and phenylmethylsulfonyl fluoride (PMSF) significantly inhibited the enzyme activity, while protease was moderately stable under freeze-thaw and refrigerated storage. CONCLUSION: The influence of fish spoilage-related enzymes, depending on various factors, is discussed in this paper. This study will provide new insight into enzymatic spoilage and its control, which can be exploited to enhance food safety and the shelf-life of fishery products worldwide. © 2018 Society of Chemical Industry.

Production, purification and biochemical characterization of a thermoactive, alkaline lipase from a newly isolated Serratia sp. W3 Tunisian strain.

A newly isolated Serratia sp. W3 strain was shown to secrete a non-induced lipase in the culture medium. Lipolytic activity was optimized using the response surface methodology (RSM) and the extracellular lipase from Serratia sp. W3 (SmL) was purified to homogeneity with a total yield of 10% and its molecular mass was estimated of about 67 kDa by SDS-PAGE. The amino acid sequence of the first 7 N-terminal residues of SmL revealed a high degree of homology with other Serratia lipase sequences. The purified SmL can be considered as thermoactive lipase, its maximal specific activity measured at pH 9 and 55 °C was shown to be 625 U/mg and 300 U/mg using tributyrin and olive oil emulsion as substrate, respectively. In contrast to other described Serratia lipases, SmL was found to be stable at a large scale of pH between pH 5 and pH 12. SmL was also able to hydrolyze its substrate in presence of various oxidizing agents as well as in presence of surfactants and some commercial detergents. Then, considering the overall biochemical properties of SmL, it can be considered as a potential candidate for industrial and biotechnological applications, such as synthesis of biodiesel and in the detergent industry.