Serratia Species Research Articles

Proteomics in the Study of Bacterial Keratitis.

Bacterial keratitis is a serious ocular infection that can cause severe visual loss if treatment is not initiated at an early stage. It is most commonly caused by Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pneumoniae, or Serratia species. Depending on the invading organism, bacterial keratitis can progress rapidly, leading to corneal destruction and potential blindness. Common risk factors for bacterial keratitis include contact lens wear, ocular trauma, ocular surface disease, ocular surgery, lid deformity, chronic use of topical steroids, contaminated ocular medications or solutions, and systemic immunosuppression. The pathogenesis of bacterial keratitis, which depends on the bacterium-host interaction and the virulence of the invading bacterium, is complicated and not completely understood. This review highlights some of the proteomic technologies that have been used to identify virulence factors and the host response to infections of bacterial keratitis in order to understand the disease process and develop improved methods of diagnosis and treatment. Although work in this field is not abundant, proteomic technologies have provided valuable information toward our current knowledge of bacterial keratitis. More studies using global proteomic approaches are warranted because it is an important tool to identify novel targets for intervention and prevention of corneal damage caused by these virulent microorganisms.

The performance characteristics of a piezoelectric ultrasonic dental scaler

The objective of this work was to investigate the performance characteristics of a piezoelectric ultrasonic dental scaler using scanning laser vibrometry. The vibration characteristics of three standard piezoelectric tips were assessed with scanning laser vibrometry under various conditions: unconstrained, under a stream of flowing water, in a water tank, as well as subjected to loads to simulate clinical conditions. Subsequently, the tips were used to disrupt an in-vitro biofilm model of dental plaque, developed using a non-pathogenic Gram-negative species of Serratia (NCIMB40259).The laser vibrometry data showed that the oscillation pattern of the ultrasonic tip depends primarily on its shape and design, as well as on the generator power. Thin tips and high power settings induce the highest vibrations. Water irrigation of the tip and loads influence the tip performance by diminishing its vibration, while water volume increases it.Serratia biofilm was disrupted by the cavitation bubbles occurring around the scaler tip. The most effective biofilm removal occurred with the thinner tip.Understanding how the ultrasonic tip oscillates when in use and how it removes dental plaque is essential for gaining more knowledge regarding the cleaning mechanisms of the ultrasonic system. Cavitation may be used to remove plaque and calculus without a mechanical contact between the dental tip and the teeth. Better knowledge would enable dental specialists to understand and improve their techniques during routine cleaning of teeth. It will also lead to improving tip design and to the production of more effective instruments for clinical use.

Serratia aquatilis sp. nov., isolated from drinking water systems.

A cream-white-pigmented, oxidase-negative bacterium (strain 2015-2462-01T), isolated from a drinking water system, was investigated in detail to determine its taxonomic position. Cells of the isolate were rod-shaped and stained Gram-negative. A comparison of the 16S rRNA gene sequence of strain 2015-2462-01T with sequences of the type strains of closely related species of the genus Serratia revealed highest similarity to Serratia fonticola (98.4 %), Serratia proteamaculans (97.8 %), Serratia liquefaciens and Serratia grimesii (both 97.7 %). 16S rRNA gene sequence similarities to all other Serratia species were below 97.4 %. Multilocus sequence analysis (MLSA) on the basis of concatenated partial gyrB, rpoB, infB and atpD gene sequences showed a clear distinction of strain 2015-2462-01T from the type strains of the closest related Serratia species. The fatty acid profile of the strain consisted of C16 : 1 ω7c, C16 : 0; C14 : 0 and C14 : 0 3-OH/iso-C16 : 1 I as major components. DNA-DNA hybridizations between 2015-2462-01T and S. fonticola ATCC 29844T resulted in a relatedness value of 27 % (reciprocal 20 %). This DNA-DNA hybridization result in combination with the MLSA results and the differential biochemical properties indicated that strain 2015-2462-01T represents a novel species of the genus Serratia, for which the name Serratia aquatilis sp. nov. is proposed. The type strain is 2015-2462-01T ( = LMG 29119T = CCM 8626T).

Transcriptomic changes in the plant pathogenic fungus Rhizoctonia solani AG-3 in response to the antagonistic bacteria Serratia proteamaculans and Serratia plymuthica.

BackgroundImproved understanding of bacterial-fungal interactions in the rhizosphere should assist in the successful application of bacteria as biological control agents against fungal pathogens of plants, providing alternatives to chemicals in sustainable agriculture. Rhizoctonia solani is an important soil-associated fungal pathogen and its chemical treatment is not feasible or economic. The genomes of the plant-associated bacteria Serratia proteamaculans S4 and Serratia plymuthica AS13 have been sequenced, revealing genetic traits that may explain their diverse plant growth promoting activities and antagonistic interactions with R. solani. To understand the functional response of this pathogen to different bacteria and to elucidate whether the molecular mechanisms that the fungus exploits involve general stress or more specific responses, we performed a global transcriptome profiling of R. solani Rhs1AP anastomosis group 3 (AG-3) during interaction with the S4 and AS13 species of Serratia using RNA-seq.ResultsApproximately 104,504 million clean 75-100 bp paired-end reads were obtained from three libraries, each in triplicate (AG3-Control, AG3-S4 and AG3-AS13). Transcriptome analysis revealed that approximately 10 % of the fungal transcriptome was differentially expressed during challenge with Serratia. The numbers of S4- and AS13-specific differentially expressed genes (DEG) were 866 and 292 respectively, while there were 1035 common DEGs in the two treatment groups. Four hundred and sixty and 242 genes respectively had values of log2 fold-change > 3 and for further analyses this cut-off value was used. Functional classification of DEGs based on Gene Ontology enrichment analysis and on KEGG pathway annotations revealed a general shift in fungal gene expression in which genes related to xenobiotic degradation, toxin and antioxidant production, energy, carbohydrate and lipid metabolism and hyphal rearrangements were subjected to transcriptional regulation.ConclusionsThis RNA-seq profiling generated a novel dataset describing the functional response of the phytopathogen R. solani AG3 to the plant-associated Serratia bacteria S4 and AS13. Most genes were regulated in the same way in the presence of both bacterial isolates, but there were also some strain-specific responses. The findings in this study will be beneficial for further research on biological control and in depth exploration of bacterial-fungal interactions in the rhizosphere.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1758-z) contains supplementary material, which is available to authorized users.

Genome sequence and comparative analysis of a putative entomopathogenic Serratia isolated from Caenorhabditis briggsae.

BackgroundEntomopathogenic associations between nematodes in the genera Steinernema and Heterorhabdus with their cognate bacteria from the bacterial genera Xenorhabdus and Photorhabdus, respectively, are extensively studied for their potential as biological control agents against invasive insect species. These two highly coevolved associations were results of convergent evolution. Given the natural abundance of bacteria, nematodes and insects, it is surprising that only these two associations with no intermediate forms are widely studied in the entomopathogenic context. Discovering analogous systems involving novel bacterial and nematode species would shed light on the evolutionary processes involved in the transition from free living organisms to obligatory partners in entomopathogenicity.ResultsWe report the complete genome sequence of a new member of the enterobacterial genus Serratia that forms a putative entomopathogenic complex with Caenorhabditis briggsae. Analysis of the 5.04 MB chromosomal genome predicts 4599 protein coding genes, seven sets of ribosomal RNA genes, 84 tRNA genes and a 64.8 KB plasmid encoding 74 genes. Comparative genomic analysis with three of the previously sequenced Serratia species, S. marcescens DB11 and S. proteamaculans 568, and Serratia sp. AS12, revealed that these four representatives of the genus share a core set of ~3100 genes and extensive structural conservation. The newly identified species shares a more recent common ancestor with S. marcescens with 99 % sequence identity in rDNA sequence and orthology across 85.6 % of predicted genes. Of the 39 genes/operons implicated in the virulence, symbiosis, recolonization, immune evasion and bioconversion, 21 (53.8 %) were present in Serratia while 33 (84.6 %) and 35 (89 %) were present in Xenorhabdus and Photorhabdus EPN bacteria respectively.ConclusionThe majority of unique sequences in Serratia sp. SCBI (South African Caenorhabditis briggsae Isolate) are found in ~29 genomic islands of 5 to 65 genes and are enriched in putative functions that are biologically relevant to an entomopathogenic lifestyle, including non-ribosomal peptide synthetases, bacteriocins, fimbrial biogenesis, ushering proteins, toxins, secondary metabolite secretion and multiple drug resistance/efflux systems. By revealing the early stages of adaptation to this lifestyle, the Serratia sp. SCBI genome underscores the fact that in EPN formation the composite end result – killing, bioconversion, cadaver protection and recolonization- can be achieved by dissimilar mechanisms. This genome sequence will enable further study of the evolution of entomopathogenic nematode-bacteria complexes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1697-8) contains supplementary material, which is available to authorized users.

Uranium Biominerals Precipitated by an Environmental Isolate of Serratia under Anaerobic Conditions.

Stimulating the microbially-mediated precipitation of uranium biominerals may be used to treat groundwater contamination at nuclear sites. The majority of studies to date have focussed on the reductive precipitation of uranium as U(IV) by U(VI)- and Fe(III)-reducing bacteria such as Geobacter and Shewanella species, although other mechanisms of uranium removal from solution can occur, including the precipitation of uranyl phosphates via bacterial phosphatase activity. Here we present the results of uranium biomineralisation experiments using an isolate of Serratia obtained from a sediment sample representative of the Sellafield nuclear site, UK. When supplied with glycerol phosphate, this Serratia strain was able to precipitate 1 mM of soluble U(VI) as uranyl phosphate minerals from the autunite group, under anaerobic and fermentative conditions. Under phosphate-limited anaerobic conditions and with glycerol as the electron donor, non-growing Serratia cells could precipitate 0.5 mM of uranium supplied as soluble U(VI), via reduction to nano-crystalline U(IV) uraninite. Some evidence for the reduction of solid phase uranyl(VI) phosphate was also observed. This study highlights the potential for Serratia and related species to play a role in the bioremediation of uranium contamination, via a range of different metabolic pathways, dependent on culturing or in situ conditions.

Bioefficacy of Serratia marcescens isolated from entomopathogenic nematodes (EPN) and their secondary metabolite prodigiosin against Spodoptera litura

Bacterial strain SH1 was isolated from entomopathogenic nematodes (EPN) Heterorhabditis indica CP16 released from insect cavaders (Spodoptera litura). Their identification by API 20E Kit as well as by 16S rDNA sequencing showed that it belongs to the species Serratia marcescens. The isolate expressed the toxicity to Spodoptera litura. In the injection assay more than 65 % insects were killed after 10 h at 23 cfu/insect; in the ingestion assay (droplet on leaf surface), more than 50 % insects were killed after 72 h at 170 cfu/cm2. The red pigment produced by the isolate SH1 was confirmed to be one of its secondary metabolites – prodigiosin based on its color, UV/VIS spectra và ESI-MS results. When injected to Spodoptera litura at a dose of 422 ng/insect, the active compound killed approximately 65 % insects after 10 h of treatment, and in the ingestion assay (droplet on the leaf surface) at a dose of 27.66 ng/cm2 killed approximately 90 % insects after 120 h of treatment.

46 Microbiological airway flora in children with cystic fibrosis in the first year of life (To treat or not to treat, that's the question!)

In children with cystic fibrosis (CF) pulmonary microbial colonization and infection are important prognostic factors. In Germany a national CF newborn screening does not exist by now and only little is known about the microbial respiratory flora of children with CF in the first years of life. In Dresden a regional newborn screening program for eastern Saxony exists since 1996. Thus, a microbiological monitoring for patients with CF was already performed from diagnosis in the first month of life throughout babyhood and we collected data from 1997 on. In the following, we want to demonstrate the microbial colonization of 55 patients in our center in their first year of life. In all patients we found bacteria other than normal flora of mouth and throat. Most commonly we detected Staphylococcus aureus, Haemophilus influenzae and Escherichia coli, but also a variety of many other such as Klebsiella, Serratia, Streptococcus, Enterobacter, Enterococcus and Acinetobacter species, Bacillus cereus, Branhamella catarrhalis, and more. We also detected Pseudomonas aeruginosa and other Pseudomonas species already in patients at this young age. In several patients we found fungi in the throat swab, such as Aspergillus , Candida and Saccharomyces species. Most of the patients needed antibiotic therapy in their first year of life due to pulmonary exacerbation, but the clinical symptoms in many cases did not correlate with the microbiological findings by throat swab. With the introduction of a national newborn screening program for CF hopefully end of this year, we will have to discuss the influence of these bacterial findings in the first year of life on the prognosis and the need for treatment.

Insect Pathogenic Bacteria in Integrated Pest Management.

The scientific community working in the field of insect pathology is experiencing an increasing academic and industrial interest in the discovery and development of new bioinsecticides as environmentally friendly pest control tools to be integrated, in combination or rotation, with chemicals in pest management programs. In this scientific context, market data report a significant growth of the biopesticide segment. Acquisition of new technologies by multinational Ag-tech companies is the center of the present industrial environment. This trend is in line with the requirements of new regulations on Integrated Pest Management. After a few decades of research on microbial pest management dominated by Bacillus thuringiensis (Bt), novel bacterial species with innovative modes of action are being discovered and developed into new products. Significant cases include the entomopathogenic nematode symbionts Photorhabdus spp. and Xenorhabdus spp., Serratia species, Yersinia entomophaga, Pseudomonas entomophila, and the recently discovered Betaproteobacteria species Burkholderia spp. and Chromobacterium spp. Lastly, Actinobacteria species like Streptomyces spp. and Saccharopolyspora spp. have gained high commercial interest for the production of a variety of metabolites acting as potent insecticides. With the aim to give a timely picture of the cutting-edge advancements in this renewed research field, different representative cases are reported and discussed.

English

The microbial profile of some concrete and earthen fish ponds within the Niger delta region was evaluated. The results of physico-chemical properties of the water samples showed that alkalinity values were significantly higher in concrete ponds (99.7±47.1 to 150±69.7) than (18±6.9 to 24±14.5 mg/L) in earthen ponds. Electrical conductivity values varied significantly between the ponds with (200±84.1 to 290±74.9 µs/m) in concrete ponds and (18±6.9 to 24±14.5 µs/m) in earthen ponds. Sulphate concentrations were higher in concrete ponds (0.25±0.36 to 1.53±14.9 mg/L) than (0.25±0.36 to 0.4±0.77 mg/L) in earthen ponds. The mean total heterotrophic bacteria count was higher in concrete ponds (6.5×105 to 7.4×105 cfu/ml) than in earthen (6.3×105 to 6.5x105 cfu/ml) ponds. The mean fungal count ranged from 2.11×105 to 2.25×105 cfu/ml in concrete pond and (1.8×105 to 2.4×105 cfu/ml) in earthen ponds. The bacterial genera isolated from the ponds were Escherichia coli, Staphylococcus sp., Aeromonas sp., Streptococcus sp., Salmonella sp., Vibrio sp., Shigella sp., Proteus sp., Pseudomonas sp., Klebsiella sp. Enterobacter species occurred only in concrete pond, while Serratia species occurred in earthen ponds. The fungal genera isolated from both the concrete and earthen ponds were Aspergillus sp., Penicillum sp. and Cladosporium sp. The genera, Fusarium sp. and Mucor sp were isolated only from earthen ponds. The study revealed that the ponds were grossly contaminated with pathogenic microorganisms which poses a risk to human health, thus of significant public health concern. Key words: Heterotrophic bacteria, fish ponds, fungal isolates, pathogens, physico-chemical properties.

Serratia marcescens lung abscess with review of a Japanese national inpatient database

Radiographic examination of an 80-year-old male patient with diabetes mellitus taking prednisolone (30 mg per day) for IgG 4 -related disease (cholangitis and pancreatitis) indicated consolidation within the lung cavity. Repeated bronchoscopies allowed us to diagnose a lung abscess caused by Serratia marcescens . Treatment with cephem antibiotics was effective, and was continued for 3 months. There was no sign of relapse. Serratia marcescens lung abscess is relatively rare, as we found only 14 cases pneumonia of Serratia species in 1.5 million cases of hospitalized patients in national administrative database of Japan.

Bacterial contamination of mobile phones of health care workers at Jimma University Specialized Hospital, Jimma, South West Ethiopia

Millions of people worldwide are suffering from infections acquired in hospitals. Contaminated equipment and hospital environments are known sources of infection. Mobile phones are used in hospitals without restrictions, regardless of their unknown microbial load. This study aimed to determine the level of bacterial contamination of mobile phones of health care workers at Jimma University Specialized Hospital in comparison with non health care workers’ mobile phones. A cross-sectional comparative study was used to conduct this study. The pattern of mobile phone use and cleaning practice of study participants were assessed using a questionnaire. Swab specimens were collected from exposed known areas of mobile phones and eluted in sterile normal saline. Colonies were counted using calibrated wire loop technique and growths were identified following standard bacteriological technique. Kirby-Bauer disc diffusion method was used to determine the antimicrobial sensitivity tests of the isolates. Data analysis was performed using SPSS version 16 A total of 71.2% (94/132) of mobile phones showed evidence of bacterial contamination from which 61.7% (58/94) were contaminated with >5colony forming units/cm2. The degree of bacterial contamination was higher among health care workers mobile phones (OR= 4.50; 95%CI 1.85-10.98). A total of 112 bacterial organisms were isolated with 33 Staphylococcus aureus, 61 coagulase negative staphylococci, 12 Bacillus species, 4 Micrococcus species, 1 Serratia species and 1 Klebsiella pneumonia. Thirty nine percent (5/13) of meticillin resistant S. aureus were vancomycin resistant. Health care workers mobile phones were more likely contaminated with meticillin resistant S. aureus than non health care workers’ mobile phones (OR=12.83; 95% CI 2.15-37.45). All of the study participants never wash their hands after mobile phone use and 75.5% (50/66) of health care workers answered that they used their mobile phones while attending patients. Health care workers mobile phones were more contaminated than non health care works’ mobile phones. The majority of the resistant isolates were from health care workers’ mobile phones.

Phenotypic and genetic characterization of rhizobia isolated from Hedysarum flexuosum in Northwest region of Morocco.

Seventy bacterial strains were isolated from root nodules of the legume Hedysarum flexuosum grown wild in soils from Northwest Morocco. Repetitive extragenic palindromic (REP)-polymerase chain reaction (PCR) clustered the strains into 30 REP-PCR groups. The nearly complete sequence of the 16S rRNA gene from a representative strain of each REP-PCR pattern showed that 17 strains were closely related to members of the genus Rhizobium of the family Rhizobiaceae of the Alphaproteobacteria. Pairwise alignments between globally aligned sequences of the 16S rRNA gene indicated that the strains from H. flexuosum had 99.75-100% identity with Rhizobium sullae type strain IS123(T). The phenotypic characteristics analyzed allowed description of a wide physiological diversity among the isolates, where the carbohydrate assimilation test was the most discriminating. Analysis of the 16S rRNA gene of a representative strains from the remaining 13 REP-PCR groups showed they belong to a wide variety of phylogenetic groups being closely related to species of genera Stenotrophomonas, Serratia, Massilia, Acinetobacter, Achromobacter, and Pseudomonas from the Beta- and Gammaproteobacteria. The R. sullae strains identified in this study produced effective symbiosis with their original host plant. None of the other bacterial strains could form nodules on H. flexuosum.

The broad-spectrum antibiotic, zeamine, kills the nematode worm Caenorhabditis elegans.

Soil bacteria can be prolific producers of secondary metabolites and other biologically active compounds of economic and clinical importance. These natural products are often synthesized by large multi-enzyme complexes such as polyketide synthases (PKSs) or non-ribosomal peptide synthases (NRPSs). The plant-associated Gram-negative bacterium, Serratia plymuthica A153, produces several secondary metabolites and is capable of killing the nematode worm Caenorhabditis elegans; a commonly used model for the study of bacterial virulence. In this study, we show that disruption of the hybrid PKS/NRPS zeamine (zmn) gene cluster results in the attenuation of “fast-killing” of C. elegans, indicating that zeamine has nematicidal activity. C. elegans also exhibits age-dependent susceptibility to zeamine, with younger worms being most sensitive to the bioactive molecule. The zmn gene cluster is widely distributed within Serratia and phytopathogenic Dickeya species and investigation of strains harboring the zmn gene cluster showed that several of them are highly virulent in C. elegans. Zeamine was described previously as a phytotoxin and broad-spectrum antibacterial compound. In addition to its nematicidal properties, we show here that zeamine can also kill Saccharomyces cerevisiae and Schizosaccharomyces pombe. The expression of the zmn gene cluster and regulation of zeamine production were also investigated. Transcription of the cluster was growth phase-dependent, and was modulated by the post-transcriptional RNA chaperone, Hfq. The results of this study show that zeamine is a highly toxic molecule with little, or no, apparent host specificity in very diverse biological systems. In its current form, zeamine(s) may be useful as a lead compound suitable for chemical modification and structure-activity assays. However, because of widespread non-selective toxicity in multiple bioassays, unmodified zeamine(s) is unlikely to be suitable as a therapeutic antibiotic.

Chronic Invasive Fungal Sinusitis Causing Pathologic LeFort I Fracture in an Immunocompetent Patient

We present the case of a 77-year-old immunocompetent woman with history of chronic rhinosinusitis who presented with pathologic LeFort I fracture after a forceful sternutation. The patient noted mild maxillary tooth discomfort following the incident and was placed on oral antibiotics, antifungals, and soft diet that failed to resolve her tooth discomfort over several months. Imaging revealed diffuse sinus opacification and LeFort type I complex fracture involving the maxilla, pterygoid plates, clivus, and right nasal bridge. There was no evidence of soft tissue swelling. The patient underwent endoscopic debridement of her sinuses, which revealed mucosal dehiscence and otherwise bleeding tissue. Frozen section was negative for fungal invasion. However, final anatomic pathology indicated necrotic bone fragments with invasive fungal hyphen. Cultures demonstrated enterococcus, burkholderia cepacia, serratia, and diphtheroid species. Fungal species were not identified from fungal cultures. The patient was started on intravenous antibiotics and antifungals for several months without significant improvement in bone healing on interval imaging. In spite of this, the stability of her palate improved on clinical examination. Chronic rhinosinusitis is associated with orbital and cranial soft tissue infectious complications but to our knowledge, this is the first report of pathologic facial fracture because of chronic invasive fungal and bacterial rhinosinusitis.

Isolation, Screening and Characterization of Effective Microbes with Potential for Biological Control of Fusarium wilt of Rock Melon

Effective microbes are a group of microorganisms that can be found in the rhizosphere, in association with plant roots which can suppress soil-borne plant pathogens directly or indirectly. A large number of bacteria including species of Alcaligenes, Arthrobacter, Bacillus, Pseudomonas, Rhizobium and Serratia have been reported to suppress the soil borne plant pathogens. In this study, Fusarium wilt symptomless Rock melon rhizospheric soil samples were collected from three locations (Malaysia). A total of seventy two effective bacteria were isolated by the dilution method. These isolates were firstly dually cultured in vitro on PDA medium with F. oxysporum f.s. melonis, the causal agent of Fusarium wilt of Rock melon. Isolates with inhibitory characteristics against the test fungus were selected for further screening by means of extracellular metabolite test. Seven isolates which showed >60% inhibition of the fungal growth was further identified on the basis of colony morphology, biochemical tests and Biolog® System. These isolates were identified as Pseudomonas sp., Bacillus sp., Serratia sp., only one isolate could not be identified. MKB04 and MKB10 gave the best suppression of Fom mycelial growth. Further molecular identification of these two isolates identified them as Bacillus amyloliquefaciens, and Alcaligenes faecalis respectively. Effective microbes are environmental friendly and in vitro antagonistic activities they manifested against F. oxysporium f. s. melonis in this study suggest that they can be used as an effective biological control agent.

Acclimatization, Isolation and Identification of Two Tetrabromobisphenol A (TBBPA) Degradation Bacteria Isolated from an Anaerobic Sludge

Two different tetrabromobisphenol A (TBBPA) degradation bacteria were isolated from an anaerobic sludge after 100 days of acclimatization, named as NJUST20 and NJUST21. Both of them are able to degrade TBBPA at 30 °C and pH 7.0. The degradation rates of NJUST20 and NJUST21 are 62.85% and 42.28%, respectively, with the initial TBBPA concentration of 10.00 mg/L. According to analysis of the 16S rDNA sequences, NJUST20 should be classified as a species of genus Enterobacter and NJUST21 as a species of genus Serratia, for which the name Enterobacter sp. NJUST20 and Serratia sp.NJUST2 are proposed.

Microbial resolution of dl-glyceric acid for l-glyceric acid production with newly isolated bacterial strains

To produce L-glyceric acid (L-GA) from DL-GA, microbial resolution was investigated using newly isolated bacterial strains capable of enantiospecific degradation of D-GA. Strains GA3R and GA72P, identified as Serratia and Pseudomonas species, respectively, exhausted D-GA within 72 h, resulting in production of L-GA with enantiomeric purity ≥89%.

Genome sequence of Serratia nematodiphila DSM 21420T, a symbiotic bacterium from entomopathogenic nematode

Serratia nematodiphila DSM 21420T (=CGMCC 1.6853T, DZ0503SBS1T), isolated from the intestine of Heterorhabditidoides chongmingensis, has been known to have symbiotic-pathogenic life cycle, on the multilateral relationships with entomopathogenic nematode and insect pest. In order to better understanding of this rare feature in Serratia species, we present here the genome sequence of S. nematodiphila DSM 21420T with the significance of first genome sequence in this species.

Molecular characterization of protease activity in Serratia sp. strain SCBI and its importance in cytotoxicity and virulence.

A newly recognized Serratia species, termed South African Caenorhabditis briggsae isolate (SCBI), is both a mutualist of the nematode Caenorhabditis briggsae KT0001 and a pathogen of lepidopteran insects. Serratia sp. strain SCBI displays high proteolytic activity, and because secreted proteases are known virulence factors for many pathogens, the purpose of this study was to identify genes essential for extracellular protease activity in Serratia sp. strain SCBI and to determine what role proteases play in insect pathogenesis and cytotoxicity. A bank of 2,100 transposon mutants was generated, and six SCBI mutants with defective proteolytic activity were identified. These mutants were also defective in cytotoxicity. The mutants were found defective in genes encoding the following proteins: alkaline metalloprotease secretion protein AprE, a BglB family transcriptional antiterminator, an inosine/xanthosine triphosphatase, GidA, a methyl-accepting chemotaxis protein, and a PIN domain protein. Gene expression analysis on these six mutants showed significant downregulation in mRNA levels of several different types of predicted protease genes. In addition, transcriptome sequencing (RNA-seq) analysis provided insight into how inactivation of AprE, GidA, and a PIN domain protein influences motility and virulence, as well as protease activity. Using quantitative reverse transcription-PCR (qRT-PCR) to further characterize expression of predicted protease genes in wild-type Serratia sp. SCBI, the highest mRNA levels for the alkaline metalloprotease genes (termed prtA1 to prtA4) occurred following the death of an insect host, while two serine protease and two metalloprotease genes had their highest mRNA levels during active infection. Overall, these results indicate that proteolytic activity is essential for cytotoxicity in Serratia sp. SCBI and that its regulation appears to be highly complex.