Genus Nocardia Research Articles

Characterization of the Flavin-Dependent Monooxygenase Involved in the Biosynthesis of the Nocardiosis-Associated Polyketide†.

Some species of the Nocardia genus harbor a highly conserved biosynthetic gene cluster designated as the NOCardiosis-Associated Polyketide (NOCAP) synthase that produces a unique glycolipid natural product. The NOCAP glycolipid is composed of a fully substituted benzaldehyde headgroup linked to a polyfunctional alkyl tail and an O-linked disaccharide composed of 3-α-epimycarose and 2-O-methyl-α-rhamnose. Incorporation of the disaccharide unit is preceded by a critical step involving hydroxylation by NocapM, a flavin monooxygenase. In this study, we employed biochemical, spectroscopic, and kinetic analyses to explore the substrate scope of NocapM. Our findings indicate that NocapM catalyzes hydroxylation of diverse aromatic substrates, although the observed coupling between NADPH oxidation and substrate hydroxylation varies widely from substrate to substrate. Our in-depth biochemical characterization of NocapM provides a solid foundation for future mechanistic studies of this enzyme as well as its utilization as a practical biocatalyst.

Evolutionary origin and functional investigation of the widely conserved plant PEBP gene STEPMOTHER OF FT AND TFL1 (SMFT).

Genes of the family PHOSPHATIDYLETHANOLAMINE-BINDING PROTEINS (PEBP) have been intensely studied in plants for their role in cell (re)programming and meristem differentiation. Recently, sporadic reports of the presence of a new type of PEBP in plants became available, highly similar to the YY-PEBPs of prokaryotes. A comprehensive investigation of their spread, origin, and function revealed conservation across the plant kingdom. The YY-PEBP clade in plants seems to have resulted from a single Horizontal Gene Transfer (HGT) episode from a prokaryotic organism to an ancestral streptophyte. YY-PEBPs are also present in other eukaryotes, such as certain fungi, diatoms, and rotifers, and these cases derive from independent HGT events. Reciprocally, the occurrence of the eukaryotic CETS/RKIP type PEBPs (CR-PEBPs) was noticed in bacteria of the genus Nocardia, showing that HGT has occurred as well from eukaryotes to prokaryotes. Based on these observations, we propose that the current model of the PEBP family in plants needs to be updated with the clade STEPMOTHER OF FT AND TFL1 (SMFT). SMFT genes not only share high sequence conservation but also show specific expression in homologous plant structures that serve as propagules. Functional analysis of Arabidopsis smft mutant lines pointed to a function for this gene in regulating seed germination, both concerning primary dormancy release and in response to adverse high-temperature conditions. Overall, our study reveals an increasing complexity in the evolutionary history of the PEBP gene family, unlocking new potential in understanding the evolution and functional spectrum of these important key regulatory genes.

Pulmonary nocardiosis caused by Nocardia arthritidis – A case report

Nocardiosis is a rare systemic infection caused by aerobic, Gram-positive filamentous bacteria that belong to the genus Nocardia, typically affecting immunocompromised individuals but can also manifest in immunocompetent people. We report a case of pulmonary nocardiosis caused by Nocardia arthritidis in a 56-year-old female with a history of recurrent respiratory illness. The patient presented with a persistent cough, on-and-off fever, and a history of pulmonary tuberculosis. Sputum analysis revealed Gram-positive beaded branching filamentous bacilli, confirmed as N. arthritidis through molecular methods. Treatment with cotrimoxazole and ceftriaxone led to symptomatic improvement.

Nocardiosis in Solid Organ Transplant Recipients: 10-Year Single Center Experience and Review of Literature.

Solid organ transplant recipients (SOTRs) are at an increased risk of nocardiosis, a rare but life-threatening opportunistic infection. Universal PCP prophylaxis with trimethoprim-sulfamethoxazole (TMP-SMX) is used at our center, which is active in vitro against most species of the Nocardia genus and may have a role in preventing early infections. This is a single-center retrospective cohort study of nocardiosis in adult SOTRs at a large transplant center between January 2012 and June 2022, with comprehensive review of literature. Out of 6179 consecutive cases, 13 (0.2%) were diagnosed with nocardiosis. The patients were predominantly male (76.9%) and kidney transplant recipients (62%). Infection was diagnosed at median of 8.8 months (range, 3.7-98) after transplant. Patients were followed for a median of 457 days (range 8-3367). Overall mortality within one year after diagnosis was 46% (6/13), of which 17% (1/6) of deaths was attributable to Nocardia infection. No recurrence was reported. Nocardia infections were noted in a small proportion of our SOTRs and carried significant morbidity and mortality. TMP-SMX prophylaxis may be protective in some cases given low incidence of cases.

Nocardia implantans sp. nov. isolated from a patient with pulmonary infection.

TwoGram-stain-positive and rod-shaped actinomycetes (strains CDC186T and CDC192) were isolated from sputum samples of a patient in Chongqing, PR China, and were investigated to determine their taxonomic status. The results of phylogenetic analysis based on the 16S rRNA gene indicated that CDC186T and CDC192 represented members of the genus Nocardia, and the sequence similarity with Nocardia beijingensis DSM 44636T was the highest, at 99.71 and 99.78 %, respectively. The DNA G+C content of both CDC186T and CDC192 was 69.1 %. Genomic diversity analysis revealed that the average nucleotide identity and in silico DNA‒DNA hybridisation values between the two novel strains and closely related species were significantly below the thresholds of 95-96 and 70 %, respectively, but these values between the two novel strains were 99.96 and 99.90 %, respectively. The phylogenetic relationship based on the dapb1 gene and the single-copy core genes further indicated that the two novel strains were clustered in separate branch adjacent to N. beijingensis DSM 44636T. Growth occurred within the ranges of 20-42 °C, pH 6.0-9.0 and NaCl concentrations of 0.5-4.5 % (w/v). The major fatty acids of CDC186T and CDC192 were C16 : 0 and C18 : 0 10-methyl [tuberculostearic acid (TBSA)]. The predominant respiratory menaquinone was MK-9. The polar lipid profile contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol mannoside, one unidentified glycolipid, one unidentified phospholipid and one unidentified phosphoglycolipid. All the genomes of the studied strains were annotated with virulence factor (VF)-associated genes homologous to those of Mycobacterium tuberculosis, and the results of susceptibility testing indicated that CDC186T and CDC192 were resistant to amoxicillin-clavulanic acid and tigecycline. On the basis of chemotaxonomic characteristics and the results of phylogenetic analyses, strains CDC186T and CDC192 represent a novel species within the genus Nocardia, for which the name Nocardia implantans sp. nov. is proposed. The type strain is CDC186T (=GDMCC 4.206T= JCM 34959T).

The first reported pulmonary nocardiosis caused by Nocardia gipuzkoensis resisted to trimethoprim/sulfamethoxazol (TMP-SMZ) in an immunocompetent patient

Nocardia gipuzkoensis was first described as a novel and distinct species in 2020 by Imen Nouioui and pulmonary nocardiosis associated with N. gipuzkoensis was once reported in two bronchiectasis patients. Noteworthy, both reported N. gipuzkoensis cases showed sensitivity to trimethoprim/sulfamethoxazol (TMP-SMZ), which are usually recommended for empirical therapy. We reported the third case of N. gipuzkoensis infection in a 16-year-old girl with chief complaints of cough and persistent chest and back pain. No underlying immuno-suppressive conditions and glucocorticoid use was revealed. Patchy lesions next to the spine and located in the posterior basal segment of the lower lobes of the left lung were seen in thorax computed tomography (CT), but no pathogenic bacteria were detected according to routine laboratory testings. Metagenomic next-generation sequencing (mNGS) combined with whole-genome sequencing (WGS) was used to classified our isolate from bronchoalveolar lavage fluid (BALF) as N. gipuzkoensis. It is worth mentioning that drug susceptibility testing of our isolate showed resistance to TMP-SMZ, which was never reported before. The patient improved remarkably both clinically and radiographically according to the treatment with imipenem-cilastatin infusion alone. mNGS and WGS showed excellent performance in identifying the Nocardia genus to the species level and improving the detection rate of N. gipuzkoensis ignored by traditional culture. Different from previously reported cases, the N. gipuzkoensis infection case showed resistance to TMP-SMZ, which is an unprecedented finding and a crucial addition to our understanding of the antibacterial spectrum of N. gipuzkoensis. The successful treatment with imipenem-cilastatin infusion alone in this case is a testament to the importance of precise identification and tailored antibiotic therapy.

VATS-visualisatie van een ernstige pulmonale infectie met Nocardia nova resistent tegen trimethoprim-sulfamethoxazol

Severe pulmonary Nocardia nova infection in a kidney transplant patient This article describes the disease course of a severe Nocardia nova infection in a patient with an underlying immunodeficiency due to a kidney transplantation, with the visualisation of Nocardia colonies in the pleural cavity through video-assisted thoracoscopic surgery. The patient was hospitalised in the emergency department with acute respiratory symptoms and respiratory failure. A CT scan of the chest revealed a massive unilateral pleural effusion with complete compressive atelectasis of the left lung. Video-assisted thoracoscopic surgery revealed bloody pleural effusion and white, nodular, pleural structures. Cultures of the biopsies grew N. nova. The empiric antibiotic treatment was switched to a combination therapy with trimethoprim-sulfamethoxazole, meropenem and a single dose of amikacin. Sensitivity testing revealed a strain of N. nova resistant to trimethoprim-sulfamethoxazole. The antibiotics were thereupon switched to linezolid and meropenem. Unfortunately, the patient died due to a refractory septic shock with multi-organ failure. Infections due to the Nocardia genus are rare and usually occur in patients with underlying immunodeficiencies. Pulmonary disease is the most frequent presentation and pleural effusion is common. Disseminated disease with central nervous system and skin involvement is also frequent. A correct microbiological diagnosis, species identification and sensitivity testing are of utmost importance because of the high intra- and interspecies differences. The strain isolated in this case had an unexpected resistance to trimethoprim-sulfamethoxazole, which is considered to be the cornerstone treatment of a Nocardia infection.

Learning from Natural Products: Study on Actinomycetes of the Genus Nocardia

The genus Nocardia comprises gram-positive bacteria, most of which are pathogenic and cause opportunistic infections of the lungs, skin, and brain in humans. Based on a collaboration study with the Medical Mycology Research Center, Chiba University, we focused on Nocardia actinomycetes as a new natural-product resource. First, by culturing (monoculture) Nocardia in various media, we isolated a new aminocyclitol nabscessin A from Nocardia abscessus IFM10029T and a new γ-lactone inohanalactone from Nocardia inohanaensis IFM0092T. On the other hand, by imitating the state in which the genus Nocardia actinomycete infects animal cells and culturing the genus in the presence of animal cells (coculture), this genus was expected to produce new compounds through interactions with the animal cells. Using mouse macrophage-like cells (J774.1) as animal cells, a new pantothenic acid amide derivative and a cyclic peptide, nocarjamide, with Wnt signal activation activity were isolated from Nocardia tenerifensis IFM10554T strain.

Draft Genome of Nocardia canadensis sp. nov. Isolated from Petroleum-Hydrocarbon-Contaminated Soil.

The bacterial strain WB46 was isolated from the rhizosphere of willow plants (Salix purpurea L.) growing in soil contaminated with petroleum hydrocarbons. The strain was subjected to whole-genome shotgun sequencing using Illumina HiSeq. Its draft genome is 7.15 Mb, with a 69.55% GC content, containing 6387 protein-coding genes and 51 tRNA and 15 rRNA sequences. The quality and reliability of the genome were assessed using CheckM, attaining an estimated genome completeness of 98.75% and an estimated contamination of 1.68%. These results indicate a high-quality genome (>95%) and low contamination (<5%). Many of these genes are responsible for petroleum hydrocarbon degradation, such as alkane 1-monooxygenase (alkB) and naphthalene dioxygenase (ndo). 16S rRNA gene analysis, including in silico DNA-DNA hybridization (DDH) and average nucleotide identity (ANI), showed that strain WB46 belongs to the genus Nocardia, and the most closely related species is Nocardia asteroides. The strain WB46 showed a distance of 63.4% and sequence identity of 88.63%, respectively. These values fall below the threshold levels of 70% and 95%, respectively, suggesting that the strain WB46 is a new species. We propose the name of Nocardia canadensis sp. nov. for this new species. Interestingly, the sequence divergence of the 16S rRNA gene showed that the divergence only occurred in the V2 region. Therefore, the conventional V3-V4, V5-V7, or V8-V9 targeting metabarcoding, among others, would not be able to assess the diversity related to this new species.

Phylogenetic reconstruction, histopathological characterization, and virulence determination of a novel fish pathogen, Nocardia brasiliensis

Nocardiosis is a prevalent disease caused by various cosmopolitan aerobic actinomycetes species within the genus Nocardia, which has been documented across diverse aquatic species. Recently, a distinctive disease manifestation resembling classical nocardiosis emerged among cultured meagre (Argyrosomus regius) along the European coastline adjacent to the North Atlantic Ocean. To identify the causative agent and reproduce the disease, we conducted experiments on specific pathogen-free (SPF) meagre specimens. Employing classical methods, we isolated bacteria from liver granulomas present in multiple diseased specimens. The causative agent was subsequently identified through a combination of differential staining, MALDI-TOF mass spectrometry (MS), genus-specific nested PCR, and sequencing of the 16S ribosomal RNA gene, which facilitated the positive identification of Nocardia brasiliensis. The isolated strain was designated as NORBRACAN1 and considered the causative agent. Remarkably, this marks the first report of this species in fish. The pathogenicity of NORBRACAN1 was further elucidated through in vivo experimentation on a cohort of 360 juvenile meagre. The intraperitoneal administration of NORBRACAN1 led to the development of internal microgranulomas without overt external signs or mortalities. Intriguingly, fish exposed to concentrations below 1 × 106 CFU ml−1 remained unaffected by mortality throughout the two-month trial period. Immunofluorescence assay unveiled the presence of viable bacteria within specific granulomas. Furthermore, our study unveiled the existence of five distinct types of microscopic granulomas characterized by necrotic centers and arranged macrophages. The formation of these granulomas was found to be contingent upon the bacterial dosage. In conclusion, our investigation demonstrates the ability of N. brasiliensis to colonize internal organs in marine fish and induce chronic granulomatosis. This research illuminates the potential pathogenesis of nocardiosis in aquatic species, underscoring the importance of N. brasiliensis as a novel causative agent in fish.

Clinical characteristics of hospitalized patients with Nocardia genus detection by metagenomic next generation sequencing in a tertiary hospital from southern China

ObjectiveAs an opportunistic pathogen, Nocardia often occurring in the immunocompromised hosts. As the unspecifc clinical presentation and low identification rate of the culture dependent methods, Nocardia infection may be under-diagnosis. Recent study have reported physicians could benefit from metagenomic next-generation sequencing (mNGS) in Nocardia diagnosis. Herein, we present patients with a positive detection of nocardiosis in mNGS, aiming to provide useful information for an differential diagnosis and patients management.MethodsA total of 3756 samples detected for mNGS from March 2019 to April 2022 at the Fifth Affifiliated Hospital of Sun Yat-sen University, were screened. Clinical records, laboratory finding, CT images and mNGS results were reviewed for 19 patients who were positive for Nocardia genus.ResultsSamples from low respiratory tract obtained by bronchoscope took the major part of the positive (15/19). 12 of 19 cases were diagnosis as Nocardiosis Disease (ND) and over half of the ND individuals (7/12) were geriatric. Nearly all of them (10/12) were immunocompetent and 2 patients in ND group were impressively asymptomatic. Cough was the most common symptom. Nocardia cyriacigeorgica (4/12) was more frequently occurring in ND, followed by Nocardia abscessus (3/12). There are 3 individuals detected more than one kind of Nocardia species (Supplementary table 1). Except one with renal failure and one allergic to sulfamethoxazole, all of them received co-sulfonamide treatment and relieved eventually.ConclusionOur study deciphered the clinical features of patients with positive nocardiosis detected by mNGS. Greater attention should be paid to the ND that occurred in the immunocompetent host and the geriatric. Due to the difficulties in establishing diagnosis of Nocardiosis disease, mNGS should play a much more essential role for a better assessment in those intractable cases. Co-sulfonamide treatment should still be the first choice of Nocardiosis disease.

Recurring nocardial mycetoma in an immunocompetent host: A rare case report

Abstract: Actinomycetoma is a chronic subcutaneous infection caused by aerobic bacteria of genus Nocardia. Nocardia species commonly affects immunocompromised patients but can rarely infect immunocompetent individuals. An agriculturist aged about 40 years presented with swelling and multiple sinuses with serous discharge on the left shoulder region. The pus sample yielded Nocardia brasiliensis by conventional culture techniques. We present a rare case of recurring nocardial mycetoma in an immunocompetent person.

Nocardia australiensis sp. nov. and Nocardia spumae sp. nov., isolated from sea foam in Queensland, Australia.

Strains USC-21046T and USC-21048T were isolated from foaming coastal marine waters on the Sunshine Coast, Queensland, Australia. Both strains displayed growth and morphological characteristics typical for members belonging to the genus Nocardia. The major polar lipids were diphosphatidylglycerol and phosphatidylethanolamine, and the major fatty acids were C16 : 0, C18 : 1 ω9c, C18 : 0 and C18 : 0 10-methyl. The mycolic acids of strains USC-21046T and USC-21048T consisted of chain lengths between 50-64 and 56-68, respectively. Moreover, both of those strains contained meso-diaminopimelic acid and ribose, arabinose, glucose and galactose as whole cell sugars. Based on the phylogenomic results, both strains belonged to the genus Nocardia with strain USC-21046T showing an 80.4 % genome similarity to N. vinacea NBRC 16497T and N. pseudovaccinii NBRC 100343T, whereas USC-21048T strain showed an 83.6 % genome similarity to N. aobensis NBRC 100429T. Both strains were delineated from their closely related relatives based on physiological (e.g. growth on sole carbon source) and chemotaxonomic (e.g. cellular fatty composition) differences. The digital DNA-DNA hybridization (dDDH) values between USC-21046T and USC-21048T and their closely related relatives were below the dDDH threshold value of ≤70 % used for the taxonomic classification of novel species status. The genome length of strains USC-21046T and USC-21048T were 6 878 863 and 7 066 978 bp, with G+C contents of 65.2 and 67.8 mol%, respectively. For the novel isolates, we propose the names Nocardia australiensis sp. nov. with the type strain USC-21046T (=DSM 111727T=NCCB 100867T) and Nocardia spumae sp. nov. with the type strain USC-21048T (=DSM 111726T=NCCB 100868T).

Screening, molecular identification, population diversity, and antibiotic susceptibility pattern of Actinomycetes species isolated from meat and meat products of slaughterhouses, restaurants, and meat stores of a developing country, Iran.

Actinomycetes can colonize surfaces of tools and equipment and can be transferred to meat and meat products during manufacture, processing, handling, and storage. Moreover, washing the meat does not eliminate the microorganisms; it only spreads them. As a result, these opportunistic pathogens can enter the human body and cause various infections. Therefore, the aim of the current study was to screen, identify, and determine the antibiotic susceptibility of Actinomycetes species from meat and meat products in the Markazi province of Iran. A total of 60 meat and meat product samples, including minced meat, mutton, beef, chicken, hamburgers, and sausages, were collected from slaughterhouses, butchers, and restaurants in the Markazi province of Iran. The samples were analyzed using standard microbiological protocols for the isolation and characterization of Actinomycetes. PCR amplification of hsp65 and 16SrRNA genes and sequence analysis of 16SrRNA were used for genus and species identification. The minimum inhibitory concentrations (MICs) of antimicrobial agents were determined by the broth microdilution method and interpreted according to the CLSI guidelines. A total of 21 (35%) Actinomycetes isolates from 5 genera and 12 species were isolated from 60 samples. The most prevalent Actinomycetes were from the genus Mycobacterium, with six (28.6%) isolates (M. avium complex, M. terrae, M. smegmatis, and M. novocastrense), followed by the genus Rhodococcus with five (23.8%) isolates (R. equi and R. erythropolis), the genus Actinomyces with four (19.1%) isolates (A. ruminicola and A. viscosus), the genus Nocardia with four (19.1%) isolates (N. asiatica, N. seriolae, and N. niigatensis), and the genus Streptomyces with two (9.5%) isolates (S. albus). Chicken and sausage samples had the highest and lowest levels of contamination, with six and one isolates. Respectively, the results of drug susceptibility testing (DST) showed that all isolates were susceptible to Ofloxacin, Amikacin, Ciprofloxacin, and Levofloxacin, whereas all of them were resistant to Doxycycline and Rifampicin. The findings suggest that meat and meat products play an important role as a reservoir for the transmission of Actinomycetes to humans, thus causing life-threatening foodborne diseases such as gastrointestinal and cutaneous disorders. Therefore, it is essential to incorporate basic hygiene measures into the cycle of meat production to ensure food safety.

Pleural effusion-related Nocardia otitidiscaviarum, Anaplasma platys and Ehrlichia canis coinfection in a dog.

The coinfections by some microorganisms have been related to severe diseases in humans and animals, where immunosuppressive agents favor opportunistic behavior of other pathogens. A 4-month-old, female mixed-breed dog with a two-week history of inappetence, prostration, emaciation, and respiratory distress was admitted at a veterinary hospital in Brazil. Tachycardia, pale mucous membranes, severe respiratory distress, and a large number of ticks (Rhipicephalus sanguineus s.l.) in different body regions were observed at clinical examination. Hematological examination of dog showed leukocytosis, neutrophilia, mild anemia, and thrombocytopenia, whereas unremarkable values in biochemical tests. Thoracic radiography revealed a pleural effusion image. Blood and the pleural fluid (purulent aspect) samples were subjected to qPCR (16S rRNA and dsb genes) and sequencing, which identified Ehrlichia canis and Anaplasma platys coinfection. An aggregate of coccoid-to-branching or long filamentous microorganisms, surrounded by pyogranulomatous inflammatory reaction was seen at the cytology of the pleural fluid. Bacteriological culture of pleural effusion showed colonies compatible with the genus Nocardia, which revealed gram-positive filamentous organisms with a tendency of fragmentation and were identified as Nocardia otitidiscaviarum in mass spectrometry (MALDI-TOF MS). Therapy of N. otitidiscaviarum isolate using levofloxacin (supported by a previous in vitro susceptibility testing) and doxycycline for E. canis and A. platys resulted in complete resolution of the clinical picture. Here, we report for the first time a triple coinfection by Nocardia otitidiscaviarum, A. platys, and E. canis in a dog with pleural effusion, where debilitating or immunosuppressive conditions induced by A. platys and E. canis coinfection probably contributed to the opportunistic behavior of N. otitidiscaviarum.

Nocardia sputorum sp. nov., an actinobacterium isolated from clinical specimens in Japan.

Two novel actinobacteria, designated IFM 12276T and IFM 12275, were isolated from clinical specimens in Japan, and their taxonomic positions were investigated using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed that strains IFM 12276 T and IFM 12275 have completely identical 16S rRNA gene sequences and were closely related to members of the genus Nocardia. The highest 16S rRNA gene sequence similarity was observed to Nocardia beijingensis (99.6 %) and Nocarida sputi (99.6 %), followed by Nocardia niwae (99.3 %) and Nocardia araoensis (99.3 %). The whole-cell hydrolysates of strains IFM 12276T and IFM 12275 contained meso-diaminopimelic acid, arabinose and galactose. The acyl type of muramic acid was N-glycolyl. The predominant isoprenoid quinone was MK-8(H4, ω-cycl.) and the principal polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannosides. Strains IFM 12276T and IFM 12275 contained mycolic acids that co-migrated with those from the type strain of N. niwae. These chemotaxonomic features corresponded to those of the genus Nocardia. Meanwhile, the differences in some phenotypic characteristics, along with the results of average nucleotide identity and digital DNA-DNA hybridization analyses, indicated that strains IFM 12276 T and IFM 12275 should be distinguished from the recognized species of the genus Nocardia. Therefore, these strains represent a novel species of the genus Nocardia, for which the name Nocardia sputorum sp. nov. is proposed. The type strain is IFM 12276T (=NBRC 115477T=TBRC 17096T).

Assessment of the mass transfer strategy and the role of the active bacterial population on the biological degradation of siloxanes

Upgrading of biogas to remove siloxanes is mandatory to meet the standards required for its use as a substitute of fossil fuels. The biological degradation of these pollutants is a low cost and environmental friendly alternative to conventional techniques, albeit certain limitations, such as the low solubility of siloxanes, still hinder its application. In the present work, two parameters were optimized in aerobic and anoxic two-phase biotrickling filters (TP-BTF): the trickling liquid velocity (TLV) and the internal gas recirculation, with the aim of improving siloxanes biological removal. The results obtained showed that the increase in TLV from 2 to 10 m h−1 resulted in higher removal efficiency (RE) under both anoxic and aerobic conditions, reaching maximum values of 55 and 47%, respectively. This effect was more significant for the linear siloxanes. On the contrary, a further increase in the TLV to 20 m h−1 together with the implementation of internal gas recirculation caused an excessive turbulence in the liquid side, detaching the biofilm and having a negative effect for the RE. The cyclic siloxanes were more effectively eliminated along the process (maximum REs of 75% were recorded for decamethylcyclopentasiloxane (D5)), but the studied system modifications exerted a minor effect on their RE. The active bacterial population involved in siloxanes degradation (studied throughout RNA extraction and sequencing) was dominated by the clade Acidithiobacillacea KCM-B-112 and the genus Parvibaculum in aerobic conditions, while the members of the family Phyllobacteriacea and the genera Nocardia and Baekduia dominated in anoxic conditions.

Assessing the growth-promoting traits of actinobacteria spp. isolated from Cleome africana: Implications on growth and root enhancement of Medicago sativa

ObjectiveEndophytes actinobacteria isolated from the Cleome africana shoot and root tissues were compared for their growth promotion (PGP) traits and their beneficial effects on shoot and root enhancement evaluated using Medicago sativa as test crop. MethodsHealthy plants of C. africana evolved for long periods on heavy metal mining sites were sampled and the resident endophytes actinobacteria communities in root and leaves tissues isolated and characterized based on their 16 s rRNA regions and a culture dependent approach. The growth-promoting traits in terms of phosphate solubilization activity, siderophore production, indole acetic acid synthesis and ACC deaminase activity, resistance to drought and salt stresses were studied for the selected endophytes. The beneficial effect of the two selected actinobacteria and their consortium in promoting growth of M. sativa plants from an inoculation assay that comprised four treatments: [a control (Con), inoculation with Streptomyces sp. (A3), inoculation with Amycolatopsis sp. (A4), and a consortium of A3+A4]. Sixty days after sowing, plants were harvested, and the biomass production was measured. ResultsThe six isolated actinobacteria strains were identified as members of the Streptomyces, Amycolatopsis and Nocardia genus. Isolates of A2 and A4 presented increased identity to A. endophytica (99.10%) and A. nivea (99.44%) respectively, isolates A1 were in the Nocardia genus, with high affinity to the N.m exicana (98.7% 16S rRNA similarity). Isolates A3 was a non-cultured and not yet identified, while the isolates A5 and A6 all from the Streptomyces genus. Isolates A6 showed high affinity S. xishensis, strain YIM M 10378, and the isolates A5 were closely related to S. nogalater (100%). Cultures of isolates A3 and A4 and their consortium was used to inoculate M. sativa and the shoot, root dry weight and total biomass (shoot+root) was higher in the inoculated plants than uninoculated ones. ConclusionThe significant increase in plant growth implies that these actinobacteria can be used as inoculants to improve crop plant growth in semi-arid regions.

The efficiency of Soran M Medium in Selective Isolation of Antibiotic Producing Actinomycetes

To assess the role of enriched constituents forming Soran M medium in selectiveisolation of antibiotic producing actinomycetes, six soil samples were collected inNovember 2016 from different sites in Soran, Erbil, Iraq. To culture soil samples spreadplatetechnique was used on Soran M and standard medium such as Arginine GlycerolSalt agar. Preliminary screening was done using cross-streak method against fourbacterial pathogenic strains and Candida albicans. Nine isolates from total 40actinomycetes isolates showed antimicrobial activities against pathogens. Themorphological and cultural characterization of these isolates was performed and showedthat 3 isolates belonged to the genus Nocardia while the others belonged to Streptomyces.The potential strain MB3 with both broad spectrum antibacterial and antifungal activitywas isolated on both media but showed different abilities to produce antibiotics. It wasidentified as Streptomyces sp. Findings from this investigation revealed that nutrientmedia with different composition affect the isolation of antibiotic producingactinomycetes with different activities.

Biodegradation of 2,4,6‐trinitrotoluene and hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine by Actinomycetes species, first time isolated and characterized from water, wastewater, and sludge

AbstractBiodegradation has been applied to remediate explosives contaminants, and bacteria have a high potential for the degradation of explosives, such as hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) and 2,4,6‐trinitrotoluene (TNT). The present study aims to screen and characterize explosive biodegradable Actinomycetes from water, wastewater, and sludge. Actinomycetes isolates were recovered from 80 environmental samples from diverse environmental resources in explosive contaminated areas of Iran and identified to the genus and species levels using conventional and molecular methods. The growth rate in the presence of pollutants and chromatography was used to determine their biodegradation capability. Twenty‐nine isolates (36.25%) of Actinomycetes were characterized from the cultured samples that belonged to 6 genus and 24 validated species. The most prevalent Actinomycetes isolated were genus Mycobacterium with 11 isolates (37.94%), genus Rhodococcus with seven isolates (24.13%), genus Nocardia with four isolates (13.8%), and genus Streptomyces with three isolates (10.33%). Moreover, our results showed that these isolates could degrade and consume 50–80% of RDX and TNT as their sole carbon and energy source. In conclusion, we showed that Actinomycetes from explosive‐contaminated areas of Iran could degrade TNT and RDX. Hence, seeking and screening untapped ecosystems that possess unexplored Actinomycetes will increase the chances of discovering the resident microorganism that has been capable of degrading TNT and RDX for application in the bioremediation process. The results of this study can be useful in using intact bacteria in nature to eliminate environmental pollution, which is one of the major environmental problems in the world.