Delftia acidovorans sepsis in a neonate with nosocomial pneumonia.

A term neonate weighing 2900 g was referred in the first week of life with complaints of abdominal distension since birth. New onset respiratory distress was noted 36 hours prior to referral. Baby required non-invasive respiratory support and intravenous antibiotics as chest X-ray was suggestive of pneumonia. Ultrasound abdomen confirmed low ano-rectal malformation treated with cut-back anoplasty. Blood culture on admission grew a rare organism Delftia acidovorans The antibiotics were tailored as per the sensitivity pattern and continued for a duration of 14 days. Respiratory distress gradually resolved by day 10 of admission. The baby developed pneumonia after 36 hours of stay in the referring hospital; most probably indicating a hospital acquired source of this pathogen. To the best of our knowledge, this is the second reported neonatal case of D. acidovorans sepsis.

Drinking-water isolated Delftia acidovorans selectively coaggregates with partner bacteria and facilitates multispecies biofilm development.

Coaggregation plays an important role in the development of multispecies biofilms in different environments, often serving as an active bridge between biofilm members and other organisms that, in their absence, would not integrate the sessile structure. The ability of bacteria to coaggregate has been reported for a limited number of species and strains. In this study, 38 bacterial strains isolated from drinking water (DW) were investigated for their ability to coaggregate, in a total of 115 pairs of combinations. Among these isolates, only Delftia acidovorans (strain 005P) showed coaggregating ability. Coaggregation inhibition studies have shown that the interactions mediating D. acidovorans 005P coaggregation were both polysaccharide-protein and protein-protein, depending on the interacting partner bacteria. Dual-species biofilms of D. acidovorans 005P and other DW bacteria were developed to understand the role of coaggregation on biofilm formation. Biofilm formation by Citrobacter freundii and Pseudomonas putida strains highly benefited from the presence of D. acidovorans 005P, apparently due to the production of extracellular molecules/public goods favouring microbial cooperation. This was the first time that the coaggregation capacity of D. acidovorans was demonstrated, highlighting its role in providing a metabolic opportunity for partner bacteria.

Whole-Genome Sequencing of a Multidrug-Resistant Strain: Delftia acidovorans B408.

BACKGROUND: Delftia acidovorans is distributed widely in the environment and has the potential to promote the growth of plants and degrade organic pollutants. However, it is also an opportunistic pathogen for human and many reports demonstrated that D. acidovorans has strong resistance to aminoglycosides and polymyxins. OBJECTIVE: The aim of this work was to reveal the antibiotic resistance genes and pathogenic genes in a novel conditional pathogenic strain-D. acidovorans B804, which was isolated from the radiation-polluted soil from Xinjiang Uyghur Autonomous Region, China. METHODS: The antibiotic resistance test was performed according to the Kirby-Bauer disk diffusion method and evaluated by the standards of the Clinical and Laboratory Standards Institute guidelines. The genome of D. acidovorans B804 was sequenced by a PacBio RS II and Illumina HiSeq 4000 platform in Shanghai Majorbio Biopharm Technology Co., Ltd. (Shanghai, China). RESULTS: The multidrug resistance phenotypes of D. acidovorans B804 was experimentally confirmed and its genome was sequenced. The total size of D. acidovorans B804 genome was 6,661,314 bp with a GC content of 66.73%. 403 genes associated with antibiotic resistances were predicted. Meanwhile, 89 pathogenic genes were also predicted and 17 of these genes might be capable of causing diseases to human, such as infections and salmonellosis. CONCLUSIONS: This genomic information can be used as a reference sequence for comparative genomic studies. The results provided more insights regarding the pathogenesis and drug resistance mechanism of D. acidovorans, which will be meaningful for developing more effective therapies toward D. acidovorans-related diseases.

Characteristics and Outcomes of Patients with Delftia acidovorans Infections: a Retrospective Cohort Study.

Delftia acidovorans (D. acidovorans) is a Gram-negative bacteria and an uncommon cause of human infections. This retrospective cohort study investigated clinical and microbiological characteristics and outcomes of patients with D. acidovorans infections. We included patients with culture-confirmed D. acidovorans infections attending Rigshospitalet, during 2002-2020. Fifty-nine patients with a median interquartile ranges (IQR) age of 47 (15-67) years were included. Thirty-five (59%) were males, and 57 (97%) had at least one comorbidity, including 25 (42%) with solid or hematologic malignancies. Eight (14%) were admitted to ICU, and 15 (25%) died within 365 days after infection. Persistent infection was found in 4 (6.8%) patients, and 41 (70%) had polymicrobial cultures, mainly with Pseudomonas spp. and Stenotrophomonas maltophilia. More than 85% of the D. acidovorans isolates were susceptible to meropenem or ceftazidime. Although, 88% and 62% of the isolates were resistant to gentamicin and colistin, respectively. D. acidovorans infections mainly affect patients with preexisting comorbidities, including malignancies. In the first year, all-cause mortality is considerable, polymicrobial cultures are common, and meropenem or cephalosporins with antipseudomonal activity could be the antibiotics of choice. IMPORTANCE Delftia acidovorans (D. acidovorans) is a Gram-negative bacteria that can cause infection in immunocompetent and immunocompromised individuals. The current knowledge comes mainly from case reports and case series. In this retrospective cohort study, we found that D. acidovorans infections mainly affect male patients with preexisting comorbidities, including malignancies. Persistent infections were not common, and most of the patients had polymicrobial cultures, mainly with Pseudomonas spp. and Stenotrophomonas maltophilia. More than 85% of the D. acidovorans isolates were susceptible to meropenem or ceftazidime. In contrast, 88% and 62% of the isolates were resistant to gentamicin and colistin, respectively.

Alkaline stress inhibits the growth of Staphylococcus epidermidis by inducing TCA cycle-triggered ROS production.

Many species of bacteria interact on the human skin to form a certain microbiome. Delftia acidovorans, a bacterium detected from human skin, inhibits the growth of S. epidermidis, a dominant bacterium of the human skin microbiota. Here, we show that ammonia secreted by D. acidovorans inhibits the growth of S. epidermidis by increasing the pH value of the medium. The pH value of D. acidovorans culture supernatant (CS) was higher than that of the medium without culture. The inhibitory activity of the D. acidovorans CS against the growth of S. epidermidis was decreased by neutralization with hydrochloric acid. Genes encoding enzymes related to ammonia production were found in the D. acidovorans genome. Moreover, the D. acidovorans CS contained a high concentration of ammonia. The addition of ammonia to S. epidermidis culture led to an increase in the reactive oxygen species (ROS) production and inhibited S. epidermidis growth. The addition of sodium hydroxide also led to an increase in the ROS production and inhibited S. epidermidis growth. The inhibitory activity of ammonia and sodium hydroxide against S. epidermidis growth was suppressed by malonic acid, an inhibitor of succinate dehydrogenase in the tricarboxylic acid (TCA) cycle, and N-acetyl-l-cysteine, a free radical scavenger. These findings suggest that D. acidovorans secretes ammonia and alkaline stress inhibits the growth of S. epidermidis by inducing TCA cycle-triggered ROS production.

Delftia acidovorans secretes substances that inhibit the growth of Staphylococcus epidermidis through TCA cycle-triggered ROS production.

The proportion of Staphylococcus aureus in the skin microbiome is associated with the severity of inflammation in the skin disease atopic dermatitis. Staphylococcus epidermidis, a commensal skin bacterium, inhibits the growth of S. aureus in the skin. Therefore, the balance between S. epidermidis and S. aureus in the skin microbiome is important for maintaining healthy skin. In the present study, we demonstrated that the heat-treated culture supernatant of Delftia acidovorans, a member of the skin microbiome, inhibits the growth of S. epidermidis, but not that of S. aureus. Comprehensive gene expression analysis by RNA sequencing revealed that culture supernatant of D. acidovorans increased the expression of genes related to glycolysis and the tricarboxylic acid cycle (TCA) cycle in S. epidermidis. Malonate, an inhibitor of succinate dehydrogenase in the TCA cycle, suppressed the inhibitory effect of the heat-treated culture supernatant of D. acidovorans on the growth of S. epidermidis. Reactive oxygen species production in S. epidermidis was induced by the heat-treated culture supernatant of D. acidovorans and suppressed by malonate. Further, the inhibitory effect of the heat-treated culture supernatant of D. acidovorans on the growth of S. epidermidis was suppressed by N-acetyl-L-cysteine, a free radical scavenger. These findings suggest that heat-resistant substances secreted by D. acidovorans inhibit the growth of S. epidermidis by inducing the production of reactive oxygen species via the TCA cycle.

Transcriptomics reveal core activities of the plant growth-promoting bacterium Delftia acidovorans RAY209 during interaction with canola and soybean roots.

The plant growth-promoting rhizobacterium Delftia acidovorans RAY209 is capable of establishing strong root attachment during early plant development at 7 days post-inoculation. The transcriptional response of RAY209 was measured using RNA-seq during early (day 2) and sustained (day 7) root colonization of canola plants, capturing RAY209 differentiation from a medium-suspended cell state to a strongly root-attached cell state. Transcriptomic data was collected in an identical manner during RAY209 interaction with soybean roots to explore the putative root colonization response to this globally relevant crop. Analysis indicated there is an increased number of significantly differentially expressed genes between medium-suspended and root-attached cells during early soybean root colonization relative to sustained colonization, while the opposite temporal pattern was observed for canola root colonization. Regardless of the plant host, root-attached RAY209 cells exhibited the least amount of differential gene expression between early and sustained root colonization. Root-attached cells of either canola or soybean roots expressed high levels of a fasciclin gene homolog encoding an adhesion protein, as well as genes encoding hydrolases, multiple biosynthetic processes, and membrane transport. Notably, while RAY209 ABC transporter genes of similar function were transcribed during attachment to either canola or soybean roots, several transporter genes were uniquely differentially expressed during colonization of the respective plant hosts. In turn, both canola and soybean plants expressed genes encoding pectin lyase and hydrolases - enzymes with purported function in remodelling extracellular matrices in response to RAY209 colonization. RAY209 exhibited both a core regulatory response and a planthost-specific regulatory response to root colonization, indicating that RAY209 specifically adjusts its cellular activities to adapt to the canola and soybean root environments. This transcriptomic data defines the basic RAY209 response as both a canola and soybean commercial crop and seed inoculant.

[Infection of the orbita due to Delftia acidovorans after a cat scratch]. / Orbita-Infektion mit Delftia acidovorans nach Katzenkratzer.

HISTORY: A 60 years old woman experienced a cat scratch 34 months ago on the left eyelid. Chronic, progredient skin lesions and headache developed. Treatments with cortisone, pimecrolimus, pregabalin and metamizole were not successful. After 24 months the patient complained of severe bulbus pain in the left eye, increased eye movement pain, and high photosensitivity. There were granulomatous papules in the area of the eye. FINDINGS AND DIAGNOSIS: The interdisciplinary examination findings and clinical-chemical parameters were inconspicuous. A biopsy of the eyelid area revealed the detection of Delftia acidovorans by bacterial 16S-rRNA-PCR. THERAPY AND COURSE: Treatment with piperacillin/tazobactam 3 × 4.5 g/d IV for 10 days led to rapid clinical improvement, so that the patient could be discharged after 11 days. After additional 10 months, she had no relapse and was free of complaints. CONCLUSIONS: D. acidovorans has not yet appeared as a zoonotic pathogen but should be included in the case of injury by animals in the differential diagnostic considerations.

Endophthalmitis due to Delftia acidovorans: An unusual ocular pathogen.

Endophthalmitis is a dreaded postoperative complication of cataract surgery. Delftia acidovorans is usually nonpathogenic and an unusual ocular pathogen. Isolated reports of delftia-associated sepsis, otitis media, endocarditis, keratitis, etc. exist in literature. We report a rare and unique case of delftia-related endophthalmitis in a 67-year-old male diagnosed 2 weeks after uneventful cataract surgery. He was treated successfully with core vitrectomy and intravitreal antibiotics. Microbiological evaluation of vitreous sample identified the causative organism as Delftia acidovorans. Post-vitrectomy fundus evaluation at 1 week revealed the presence of retinal vascular sheathing and sclerosis along with few retinal hemorrhages. Final visual recovery was poor due to the presence of macular edema, epiretinal membrane, and temporal disc pallor.

Delftia acidovorans pseudo outbreak in portable reverse osmosis machines: Interventions to ensure safe and cost-effective hemodialysis.

INTRODUCTION: Reverse osmosis (RO), a major advance in hemodialysis (HD) safety, effectively clears most water organisms. Delftia acidovorans is an environmental water-borne pathogen that is rarely reported to cause human infections. We report a pseudo outbreak caused by colonization of RO machines with D acidovorans with no reported human infections and interventions to improve HD safety. METHODS: Repeated positive RO product water cultures triggered our hospital to initiate an investigation, RO machines were examined for mechanical integrity by biomedical engineers. Cultures of product water as well as RO parts were done. Testing for bacterial relatedness after identification was performed. An investigation was conducted in a systematic fashion to determine the cause and the extent of the problem. RESULTS: Upon formal review of policies and procedures, there were minor deficiencies. Rectifying these deviations from policies did not stop the repeated positive water cultures. A 7-step investigation and correction was successfully conducted. City water testing with filtration and concentration methods was positive for D acidovorans. Major renovation of the HD unit with replacement of all RO machines and a 2-step water filtration resulted in elimination of the pseudo outbreak. CONCLUSION: City water was the source of biofilm formation of D acidovorans in RO machines that was not possible to eradicate. Application of incoming water filters was an effective preventive strategy. Replacement of RO machines after 4 failed disinfection attempts is the most cost-effective strategy as well for persistent positive water cultures. The HD remains RO water culture negative 2 years after changes.

Adhesion of Pseudomonas aeruginosa, Achromobacter xylosoxidans, Delftia acidovorans, Stenotrophomonas maltophilia to contact lenses under the influence of an artificial tear solution.

Corneal infection is a devastating sight-threatening complication that is associated with contact lens (CL) wear, commonly caused by Pseudomonas aeruginosa. Lately, Achromobacter xylosoxidans, Delftia acidovorans, and Stenotrophomonas maltophilia have been associated with corneal infection. This study investigated the adhesion of these emerging pathogens to CLs, under the influence of an artificial tear solution (ATS) containing a variety of components commonly found in human tears. Two different CL materials, etafilcon A and senofilcon A, either soaked in an ATS or phosphate buffered saline, were exposed to the bacteria. Bacterial adhesion was investigated using a radio-labeling technique (total counts) and plate count method (viable counts). The findings from this study revealed that in addition to P. aeruginosa, among the emerging pathogens evaluated, A. xylosoxidans showed an increased propensity for adherence to both CL materials and S. maltophilia showed lower viability. ATS influenced the viable counts more than the total counts on CLs.

Urine nitrification with a synthetic microbial community.

During long-term extra-terrestrial missions, food is limited and waste is generated. By recycling valuable nutrients from this waste via regenerative life support systems, food can be produced in space. Astronauts' urine can, for instance, be nitrified by micro-organisms into a liquid nitrate fertilizer for plant growth in space. Due to stringent conditions in space, microbial communities need to be be defined (gnotobiotic); therefore, synthetic rather than mixed microbial communities are preferred. For urine nitrification, synthetic communities face challenges, such as from salinity, ureolysis, and organics. In this study, a synthetic microbial community containing an AOB (Nitrosomonas europaea), NOB (Nitrobacter winogradskyi), and three ureolytic heterotrophs (Pseudomonas fluorescens, Acidovorax delafieldii, and Delftia acidovorans) was compiled and evaluated for these challenges. In reactor 1, salt adaptation of the ammonium-fed AOB and NOB co-culture was possible up to 45mScm-1, which resembled undiluted nitrified urine, while maintaining a 44±10mgNH4+-NL-1d-1 removal rate. In reactor 2, the nitrifiers and ureolytic heterotrophs were fed with urine and achieved a 15±6mg NO3--NL-1d-1 production rate for 1% and 10% synthetic and fresh real urine, respectively. Batch activity tests with this community using fresh real urine even reached 29±3mgNL-1d-1. Organics removal in the reactor (69±15%) should be optimized to generate a nitrate fertilizer for future space applications.

Detecting Gold Biomineralization by Delftia acidovorans Biofilms on a Quartz Crystal Microbalance.

The extensive use of gold in sensing, diagnostics, and electronics has led to major concerns in solid waste management since gold and other heavy metals are nonbiodegradable and can easily accumulate in the environment. Moreover, gold ions are extremely reactive and potentially harmful for humans. Thus, there is an urgent need to develop reliable methodologies to detect and possibly neutralize ionic gold in aqueous solutions and industrial wastes. In this work, by using complementary measurement techniques such as quartz crystal microbalance (QCM), atomic force microscopy, crystal violet staining, and optical microscopy, we investigate a promising biologically induced gold biomineralization process accomplished by biofilms of bacterium Delftia acidovorans. When stressed by Au3+ ions, D. acidovorans is able to neutralize toxic soluble gold by excreting a nonribosomal peptide, which forms extracellular gold nanonuggets via complexation with metal ions. Specifically, QCM, a surface-sensitive transducer, is employed to quantify the production of these gold complexes directly on the D. acidovorans biofilm in real time. Detailed kinetics obtained by QCM captures the condition for maximized biomineralization yield and offers new insights underlying the biomineralization process. To the best of our knowledge, this is the first study providing an extensive characterization of the gold biomineralization process by a model bacterial biofilm. We also demonstrate QCM as a cheap, user-friendly sensing platform and alternative to standard analytical techniques for studies requiring high-resolution quantitative details, which offers promising opportunities in heavy-metal sensing, gold recovery, and industrial waste treatment.

Delftia acidovorans pneumonia with lung cavities formation / Neumonia con formación de cavidades pulmonares causada por Delftia acidovorans

Abstract Case Description: A 52-year-old female patient was admitted to our clinic with complaints of cough, sputum, fever and fatigue. The patient has been receiving immunosuppressive therapy for thrombocytopenic purpura for 5 years. Clinical Finding: Inspiratory crackles were heard on both hemithorax. Oxygen saturation measured with the pulse oximeter was 97%. Chest X-ray showed diffuse reticular opacities that were more prominent in the upper zones of both lungs. WBC counts were 17,600 mm3 and Platelet counts were 29,000 mm3. Thorax CT showed that there were many thin-walled cavities and millimetric nodules accompanied by ground-glass infiltrates in the upper and middle lobes. Gram staining of bronchial fluid, taken by bronchoscopy, revealed Gram-negative bacilli and intense polymorphonuclear leukocytes. The bacteria were defined as Delftia acidovorans by BD Phoenix automated system. Treatment and outcomes: The patient was hospitalized with suspicion of opportunistic pulmonary infections and cavitary lung disease. After the empirical treatment of intravenous piperacillin-tazobactam and oral clarithromycin, her clinical and radiological findings significantly regressed, and she was discharged with outpatient follow-up. Clinical Relevance: This is the first example of cavitary pneumonia due to Delftia acidovorans in an immunocompromised patient. We would like to emphasize that Delftia pneumonia should be considered in the differential diagnosis of pulmonary cavitary involvement in such patients.

Resumen Descripción del caso: Una mujer de 52 años llegó a la clínica con tos, esputo, fiebre y fatiga. El paciente estuvo recibiendo terapia inmunosupresora durante 5 años para el tratamiento de la púrpura trombocitopénica. Hallazgo clínico: se escucharon crepitaciones inspiratorias en ambos hemitórax. La saturación de oxígeno fue del 97%. La radiografía de tórax mostró opacidades reticulares difusas que eran más prominentes en las zonas superiores de ambos pulmones. Los recuentos de leucocitos fueron de 17,600 mm3 y los recuentos de plaquetas fueron de 29,000 mm3. La TC de tórax mostró muchas cavidades de pared delgada y nódulos milimétricos acompañados de infiltrados vitrales en los lóbulos superior y medio. La tinción de Gram del líquido bronquial reveló bacilos gramnegativos y leucocitos polimorfonucleares. Las bacterias fueron identificadas como Delftia acidovorans. Tratamiento y resultados: La paciente fue hospitalizado con una sospecha de infección oportunista pulmonar y enfermedad pulmonar cavitaria. Después del tratamiento empírico de piperacilina-tazobactam intravenosa y claritromicina oral, los síntomas y signos retrocedieron significativamente, y fue dada de alta con seguimiento ambulatorio. Relevancia clínica: este es el primer registro de neumonía cavitaria causado por Delftia acidovorans en una paciente inmunocomprometida. Enfatizamos que la neumonía por Delftia debe considerarse en el diagnóstico diferencial de la afectación de la cavidad pulmonar en tales pacientes.

Combined effects of mutualistic rhizobacteria counteract virus-induced suppression of indirect plant defences in soya bean.

It is increasingly clear that microbial plant symbionts can influence interactions between their plant hosts and other organisms. However, such effects remain poorly understood, particularly under ecologically realistic conditions where plants simultaneously interact with diverse mutualists and antagonists. Here, we examine how the effects of a plant virus on indirect plant defences against its insect vector are influenced by co-occurrence of other microbial plant symbionts. Using a multi-factorial design, we manipulated colonization of soya bean using three different microbes: a pathogenic plant virus (bean pod mottle virus (BPMV)), a nodule-forming beneficial rhizobacterium ( Bradyrhizobium japonicum) and a plant growth-promoting rhizobacterium ( Delftia acidovorans). We then assessed recruitment of parasitoids ( Pediobious foveolatus (Eulophidae)) and parasitism rates following feeding by the BPMV vector Epilachna varivestis (Coccinellidae). BPMV infection suppressed parasitoid recruitment, prolonged parasitoid foraging time and reduced parasitism rates in semi-natural foraging assays. However, simultaneous colonization of BPMV-infected hosts by both rhizobacteria restored parasitoid recruitment and rates of parasitism to levels similar to uninfected controls. Co-colonization by the two rhizobacteria also enhanced parasitoid recruitment in the absence of BPMV infection. These results illustrate the potential of plant-associated microbes to influence indirect plant defences, with implications for disease transmission and herbivory, but also highlight the potential complexity of such interactions.

Delftia acidovorans pneumonia with lung cavities formation.

CASE DESCRIPTION: A 52-year-old female patient was admitted to our clinic with complaints of cough, sputum, fever and fatigue. The patient has been receiving immunosuppressive therapy for thrombocytopenic purpura for 5 years. CLINICAL FINDING: Inspiratory crackles were heard on both hemithorax. Oxygen saturation measured with the pulse oximeter was 97%. Chest X-ray showed diffuse reticular opacities that were more prominent in the upper zones of both lungs. WBC counts were 17,600 mm3 and Platelet counts were 29,000 mm3. Thorax CT showed that there were many thin-walled cavities and millimetric nodules accompanied by ground-glass infiltrates in the upper and middle lobes. Gram staining of bronchial fluid, taken by bronchoscopy, revealed Gram-negative bacilli and intense polymorphonuclear leukocytes. The bacteria were defined as Delftia acidovorans by BD Phoenix automated system. TREATMENT AND OUTCOMES: The patient was hospitalized with suspicion of opportunistic pulmonary infections and cavitary lung disease. After the empirical treatment of intravenous piperacillin-tazobactam and oral clarithromycin, her clinical and radiological findings significantly regressed, and she was discharged with outpatient follow-up. CLINICAL RELEVANCE: This is the first example of cavitary pneumonia due to Delftia acidovorans in an immunocompromised patient. We would like to emphasize that Delftia pneumonia should be considered in the differential diagnosis of pulmonary cavitary involvement in such patients.

DESCRIPCIÓN DEL CASO: Una mujer de 52 años llegó a la clínica con tos, esputo, fiebre y fatiga. El paciente estuvo recibiendo terapia inmunosupresora durante 5 años para el tratamiento de la púrpura trombocitopénica. HALLAZGO CLÍNICO: se escucharon crepitaciones inspiratorias en ambos hemitórax. La saturación de oxígeno fue del 97%. La radiografía de tórax mostró opacidades reticulares difusas que eran más prominentes en las zonas superiores de ambos pulmones. Los recuentos de leucocitos fueron de 17,600 mm3 y los recuentos de plaquetas fueron de 29,000 mm3. La TC de tórax mostró muchas cavidades de pared delgada y nódulos milimétricos acompañados de infiltrados vitrales en los lóbulos superior y medio. La tinción de Gram del líquido bronquial reveló bacilos gramnegativos y leucocitos polimorfonucleares. Las bacterias fueron identificadas como Delftia acidovorans. TRATAMIENTO Y RESULTADOS: La paciente fue hospitalizado con una sospecha de infección oportunista pulmonar y enfermedad pulmonar cavitaria. Después del tratamiento empírico de piperacilina-tazobactam intravenosa y claritromicina oral, los síntomas y signos retrocedieron significativamente, y fue dada de alta con seguimiento ambulatorio. RELEVANCIA CLÍNICA: este es el primer registro de neumonía cavitaria causado por Delftia acidovorans en una paciente inmunocomprometida. Enfatizamos que la neumonía por Delftia debe considerarse en el diagnóstico diferencial de la afectación de la cavidad pulmonar en tales pacientes.

New Crystallographic Snapshots of Large Domain Movements in Bacterial 3-Hydroxy-3-methylglutaryl Coenzyme A Reductase.

The enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (HMGR) catalyzes the first committed step of the mevalonate pathway, which is used across biology in the biosynthesis of countless metabolites. HMGR consumes 2 equiv of the cofactor NAD(P)H to perform the four-electron reduction of HMG-CoA to mevalonate toward the production of steroids and isoprenoids, the largest class of natural products. Recent structural data have shown that HMGR contains a highly mobile C-terminal domain (CTD) that is believed to adopt many different conformations to permit binding and dissociation of the substrate, cofactors, and products at specific points during the reaction cycle. Here, we have characterized the HMGR from Delftia acidovorans as an NADH-specific enzyme and determined crystal structures of the enzyme in unbound, mevalonate-bound, and NADH- and citrate-bound states. Together, these structures depict ligand binding in both the active site and the cofactor-binding site while illustrating how a conserved helical motif confers NAD(P)H cofactor specificity. Unexpectedly, the NADH-bound structure also reveals a new conformation of the CTD, in which the domain has "flipped" upside-down, while directly binding the cofactor. By capturing these structural snapshots, this work not only expands the known range of HMGR domain movement but also provides valuable insight into the catalytic mechanism of this biologically important enzyme.

The Sequence of Two Bacteriophages with Hypermodified Bases Reveals Novel Phage-Host Interactions.

Bacteriophages SP-15 and ΦW-14 are members of the Myoviridae infecting Bacillus subtilis and Delftia (formerly Pseudomonas) acidovorans, respectively. What links them is that in both cases, approximately 50% of the thymine residues are replaced by hypermodified bases. The consequence of this is that the physico-chemical properties of the DNA are radically altered (melting temperature (Tm), buoyant density and susceptibility to restriction endonucleases). Using 454 pyrosequencing technology, we sequenced the genomes of both viruses. Phage ΦW-14 possesses a 157-kb genome (56.3% GC) specifying 236 proteins, while SP-15 is larger at 222 kb (38.6 mol % G + C) and encodes 318 proteins. In both cases, the phages can be considered genomic singletons since they do not possess BLASTn homologs. While no obvious genes were identified as being responsible for the modified base in ΦW-14, SP-15 contains a cluster of genes obviously involved in carbohydrate metabolism.

Metal tolerance assisted antibiotic susceptibility profiling in Comamonas acidovorans.

Metal ions are known selective agents for antibiotic resistance and frequently accumulate in natural environments due to the anthropogenic activities. However, the action of metals that cause the antibiotic resistance is not known for all bacteria. The present work is aimed to investigate the co-selection of metals and antibiotic resistance in Comamonas acidovorans. Tolerance profile of 16 metals revealed that the strain could tolerate high concentrations of toxic metals i.e., Cr (710 ppm), As (380 ppm), Cd (320 ppm), Pb (305 ppm) and Hg (205 ppm). Additionally, metal tolerant phenotypes were subjected to antibiotic resistance profiling; wherein several metal tolerant phenotypes (Cr 1.35-fold; Co-1.33 fold; Mn-1.29 fold) were resistant, while other metal tolerant phenotypes (Mg 1.32-fold; Hg 1.29-fold; Cu 1.28-fold) were susceptible than control phenotype. Metal accumulation may alter the metabolism of C. acidovorans that activates or inactivates the genes responsible for antibiotic resistance, resulting in the resistance and/or susceptibility pattern observed in metal resistant phenotypes.