Luteus Strain Research Articles

Pathogenetic characterization of a Micrococcus luteus strain isolated from an infant.

To explore the clinical characteristics of Micrococcus luteus bloodstream infection in an infant and characterize the phenotype and genotype of the isolated strains, as well as seek suitable infection models for assessing virulence. Clinical data was collected from an infant patient diagnosed with M. luteus bloodstream infection. Metagenomic sequencing was performed on the isolated blood sample. The strain was isolated and underwent mass spectrometry, biochemical tests, antibiotic susceptibility assays, and whole-genome sequencing. The Galleria mellonella infection model was used to assess M. luteus virulence. Patient responded poorly to cephalosporins, but recovered after Linezolid treatment. Metagenomic sequencing identified M. luteus as the predominant species in the sample, confirming infection. They were identified as M. luteus with a high confidence level of 98.99% using mass spectrometry. The strain showed positive results for Catalase, Oxidase, and Urea tests, and negative results for Mannose, Xylose, Lactose, Mannitol, Arginine, and Galactose tests, consistent with the biochemical profile of M. luteus reference standards. M. luteus susceptibility to 15 antibiotics was demonstrated and no resistance genes were detected. Predicted virulence genes, including clpB, were associated with metabolic pathways and the type VI secretion system. The infection model demonstrated dose-dependent survival rates. The infant likely developed a bloodstream infection with M. luteus due to compromised immunity. Although the isolated strain is sensitive to cephalosporin antibiotics and has low pathogenicity in infection models, clinical treatment with cephalosporins was ineffective. Linezolid proved to be effective, providing valuable guidance for future clinical management of such rare infections.

Synthesis of Tetracyclic Spirooxindolepyrrolidine-Engrafted Hydantoin Scaffolds: Crystallographic Analysis, Molecular Docking Studies and Evaluation of Their Antimicrobial, Anti-Inflammatory and Analgesic Activities

In a sustained search for novel potential drug candidates with multispectrum therapeutic application, a series of novel spirooxindoles was designed and synthesized via regioselective three-component reaction between isatin derivatives, 2-phenylglycine and diverse arylidene-imidazolidine-2,4-diones (Hydantoins). The suggested stereochemistry was ascertained by an X-ray diffraction study and NMR spectroscopy. The resulting tetracyclic heterocycles were screened for their in vitro and in vivo anti-inflammatory and analgesic activity and for their in vitro antimicrobial potency. In vitro antibacterial screening revealed that several derivatives exhibited remarkable growth inhibition against different targeted microorganisms. All tested compounds showed excellent activity against the Micrococccus luteus strain (93.75 µg/mL ≤ MIC ≤ 375 µg/mL) as compared to the reference drug tetracycline (MIC = 500 µg/mL). Compound 4e bearing a p-chlorophenyl group on the pyrrolidine ring exhibited the greatest antifungal potential toward Candida albicans and Candida krusei (MIC values of 23.43 µg/mL and 46.87 µg/mL, respectively) as compared to Amphotericin B (MIC = 31.25 and 62.50 µg/mL, respectively). The target compounds were also tested in vitro against the lipoxygenase-5 (LOX-5) enzyme. Compounds 4i and 4l showed significant inhibitory activity with IC50 = 1.09 mg/mL and IC50 = 1.01 mg/mL, respectively, more potent than the parent drug, diclofenac sodium (IC50 = 1.19 mg/mL). In addition, in vivo evaluation of anti-inflammatory and analgesic activity of these spirooxindoles were assessed through carrageenan-induced paw edema and acetic acid-induced writhing assays, respectively, revealing promising results. In silico molecular docking and predictive ADMET studies for the more active spirocompounds were also carried out.

Electrochemical Parameters of Microbial Fuel Cells Based on the Micrococcus luteus Strain, New Ion-Exchange Membranes and Various Sugars

Electrochemical Parameters of Microbial Fuel Cells Based on the Micrococcus luteus Strain, New Ion-Exchange Membranes and Various Sugars

Anti-urolithiatic, antibacterial, anti-inflammatory and analgesic effects of Erica arborea flowers and leaves hydromethanolic extracts: An ethnopharmacological study

Erica arborea L. is a medicinal plant vastly used in therapeutic purposes in several parts of the world for antimicrobial, anti-inflammatory, and diuretic purposes, and in treating urinary infections and kidney stones. The current investigation aimed to evaluate the medicinal use ofE. arboreain Algeria's Bejaia region, and to examine the anti-urolithiatic, antibacterial, anti-inflammatory (in vivo), analgesic, and toxicity effects ofE. arboreahydromethanolic extracts from leaves (EALE) and flowers (EALE) to give a justification for its use in the traditional medicine. The in vitro anti-urolithiathic activity of E. arborea leaf and flower hydromethanolic extracts nucleation and aggregation of crystals were measured using spectrophotometric methods. The agar disk diffusion assay and minimum inhibitory concentration (MIC) determination were employed to estimate the antibacterial effect of EAME against three Gram-positive and three Gram-negative bacterial strains in vitro. In addition, the xylene and croton oil-induced ear edema methods in mice were used to examine the topical and oral anti-inflammatory potential of the extracts. Similarly, the analgesic effect of the extract was assessed via the acetic acid-induced abdominal constriction in mice, whereas the acute toxicity of EAME was conducted following OECD guidelines.An ethnobotanical survey was conducted among 171 informants with 212 questionnaire cards. Results indicated that 28.04 % of people in the studied region usedE. arboreain traditional folk medicine. Additionally, results revealed the presence of epicatechin, palmitic acid, and kaempferol-3-O-glucoside in the plant extracts. Results also showed that EAME exhibits significant anddose-dependent anti-urolithiatic activity in nucleation and aggregation assays. Furthermore, results revealed that the extracts exhibit significant antibacterial activity. The E. arborea flower extract (EAFE) showed maximum antibacterial activity, especially against P. aeruginosa, E. coli, S. gallinarum, and B. cereus. In addition, a greater minimum inhibitory concentration (MIC) in this extract was found at 1.60 mg/mL against M. luteus strain compared to the positive control. Moreover, the EAME caused a significant inhibition influence in the xylene and croton oil-induced edematous in mice. In contrast, the topical anti-inflammatory potential showed that extracts exhibit a considerable anti-edematogenic effect in both animal models. In the writhing reaction induced by the acetic acid model, the two extracts significantly reduced abdominal contractions. Finally, results of the toxicity assay showed that EAME is safe and no deaths or changes in mice behavior were observed even when doses as high as 5 g/kg DW were used. From the ethnopharmacological studies, our consequences endorse the benefit of E. arboreain folk medicine. Results of this investigation suggest that the leaf and flower extracts of E. arborea exhibit notable anti-urolithiatic, anti-inflammatory, analgesic, and antibacterial activities and are safe as a natural source of drugs with the above effects.

Bioproduction and Application of Orange and Yellow Pigments Obtained from Chryseomicrobium palamuruense and Micrococcus luteus

Colour is a fundamental and most likely one of the primary attributes to be observed by the human senses, making it an essential part of human life and culture. This study investigates the bioproduction and potential application of bacterial pigments obtained from abattoir wastewater. Bacteria isolates recovered from abattoir wastewater were screened for pigment production and identified using the 16S rRNA gene sequence. Optimal physicochemical conditions of parameters were investigated and harnessed for bulk pigment production. Pigments produced were characterised using UV-Visible Spectrophotometer and Fourier Transform Infra-Red (FTIR) Analysis. The antibacterial and dyeing ability of the extracted pigments were evaluated. Two bacteria namely, Chryseomicrobium palamuruense strain PUI and Micrococcus luteus strain 1k produced orange and yellow pigments respectively. The UV-visible spectrum of the orange pigment produced by Chryseomicrobium palamuruense showed surface plasmon resonance peaks at 262, 426, and 453 nm while that of the yellow pigment produced by Micrococcus luteus showed a single peak at 260 nm. The FTIR analysis of the extracted pigments indicated the presence of some functional groups namely hydroxyl (OH), C-H, primary and secondary C-O, and skeletal C-C vibrations. Chryseomicrobium palamuruense and Micrococcus luteus showed no antibacterial activity against the selected typed bacterial isolates assessed in this study. The orange pigment extracted from Chryseomicrobium palamuruense was retained on cotton and polyester producing different shades of colour on the two fabrics when used as a dyeing agent. The pigment-producing potentials of these organisms suggest their relevance as promising dyes in textile industry.

Single and co-inoculum of endophytic bacteria promote growth and yield of Jerusalem artichoke through upregulation of plant genes under drought stress.

Helianthus tuberosus L. (Jerusalem artichoke) produce inulin, a type of fructan, which possesses several biotechnology applications, e.g., sugar syrup, prebiotics, fiber in diabetic food, enabling blood sugar and cholesterol reduction. Drought reduces inulin accumulation in the tubers of Jerusalem artichoke as the plants protect themselves from this stress by induction of stress gene responses, effecting growth reduction. Endophytic bacteria are promising candidates to promote plant growth and yield particularly under abiotic stress. Therefore, three endophytic bacteria with plant growth promoting properties were examined for their ability to improve Jerusalem artichoke growth and yield under both well-watered and drought conditions when inoculated individually or in combinations in pot experiments with 2 factorial random complete block design. The interactions of the endophytic bacteria and plant host determined the differential gene expression in response to drought as revealed by quantitative polymerase chain reaction. Single inoculum of the endophytic bacteria increased the height, weight, root traits, and harvest index of Jerusalem artichoke compared to co-inocula under both well-watered and drought conditions. However, the co-inocula of Rossellomorea aquimaris strain 3.13 and Bacillus velezensis strain 5.18 proved to be a synergistic combination leading to high inulin accumulation; while the co-inocula of B. velezensis strain 5.18 and Micrococcus luteus strain 4.43 were not beneficial when used in combination. The genes, dehydrin like protein and ethylene responsive element binding factor, were upregulated in the plants inoculated with single inoculum and co-inocula of all endophytic bacteria during drought stress. Moreover, the gene expression of indole-3-acetic acid (IAA) amido synthetase were up-regulated in Jerusalem artichoke inoculated with M. luteus strain 4.43 during drought stress. The fructan:fructan 1-fructosyltransferase (1-FFT) was also stimulated by the endophytic bacteria particularly in drought condition; the results of this study could explain the relationship between endophytic bacteria and plant host for growth and yield promotion under well-watered and drought conditions.

Toxic heavy metal/oxyanion tolerance in haloarchaea from some saline and hypersaline ecosystems.

Toxic heavy metal/oxyanion contamination has increased severely through the last decades. In this study, 169 native haloarchaeal strains were isolated from different saline and hypersaline econiches of Iran. After providing pure culture and performing morphological, physiological, and biochemical tests, haloarchaea resistance toward arsenate, selenite, chromate, cadmium, zinc, lead, copper, and mercury were surveyed using an agar dilution method. On the basis of minimum inhibitory concentrations (MICs), the least toxicities were found with selenite and arsenate, while the haloarchaeal strains revealed the highest sensitivity for mercury. On the other hand, the majority of haloarchaeal strains exhibited similar responses to chromate and zinc, whereas the resistance level of the isolates to lead, cadmium, and copper was very heterogeneous. 16 S ribosomal RNA (rRNA) gene sequence analysis revealed that most haloarchaeal strains belong to the Halorubrum and Natrinema genera. The obtained results from this study showed that among the identified isolates, Halococcus morrhuae strain 498 had an exceptional resistance toward selenite and cadmium (64 and 16 mM, respectively). Also, Halovarius luteus strain DA5 exhibited a remarkable tolerance against copper (32 mM). Moreover, strain Salt5, identified as Haloarcula sp., was the only strain that could tolerate all eight tested heavy metals/oxyanions and had a significant tolerance of mercury (1.5 mM).

Evaluation of the Preliminary Safety, Tolerability and Colonisation Efficacy of Topical Probiotic Formulations Containing Micrococcus luteus Q24 in Healthy Human Adults

Probiotics developed for topical applications in humans have the potential to beneficially modulate microbial imbalances on the skin surface and thereby improve skin health. This study was conducted to determine whether topical formulations containing the human skin commensal Micrococcus luteus strain Q24 (BLIS Q24) are safe, tolerable and efficacious when used by healthy human subjects. M. luteus Q24 was assessed in vitro for haemolytic activity and its antibiotic susceptibility profile. Formulations of strain Q24 were evaluated for the preliminary safety and tolerability in healthy human participants. Forty-seven adults were randomly assigned to four single-site, single-blind randomised placebo or baseline controlled or active-controlled trials. Skin swab samples were collected for differential viable counts to monitor levels of probiotic colonisation. M. luteus Q24 was found to be non-haemolytic and susceptible to commonly used antibiotics. The M. luteus Q24 formulations were safe and tolerable and >90% of the participants reported improvements from baseline in the appearance (e.g., radiance and hydration) of their treated skin. Additionally, participants observed a reduction in pore size, skin clarity and enhanced skin softness. No adverse effects were reported. A dose-related significant increase was observed in the levels of M. luteus Q24 isolated from skin swabs of the probiotic-treated subjects. Placebo-controlled trials in human subjects involving the topical application of different doses of M. luteus Q24 formulations were supportive of the safety, tolerability and efficacy of probiotic M. luteus Q24. Self-reported skin health assessments by the subjects indicated that M. luteus Q24 has good potential as a probiotic for improving skin health quality.

Biofouling Control in an Anaerobic Membrane Bioreactor with Indigenous Quorum Quenching Bacterium Micrococcus luteus Strain AnQ-m1

This study isolated and screened indigenous strains quenching the acyl homoserine lactone (AHL)-mediated quorum sensing system and investigated the effectiveness of a selected strain for biofouling control in a laboratory-scale anaerobic membrane bioreactor (AnMBR). Among the 11 facultative anaerobes isolated from anaerobic sludge, Micrococcus luteus strain AnQ-m1 was screened out as the most potent AHL degrader. Its AHL degradability was further examined while encapsulating the cells in polysulfone–alginate beads to optimize the encapsulation medium recipe. The QQ beads with immobilized AnQ-m1 cells retarded the apparent membrane fouling rate by 2.2 times compared with the AnMBR with vacant beads. C8-HSL, the dominant AHL in AnMBRs, was effectively (∼70%) quenched in the QQ-AnMBR before the membrane was fouled; however, its concentration was increased to the normal level when the membrane was fouled. Polysaccharides in a loosely bound extracellular polymeric substance were gradually reduced at a constant rate during the QQ stage, while the indigenous QQ strain barely affected the microbial community structure of the bulk sludge and the water treatment performance of the AnMBR. These findings provide new insights into the QQ-based biofouling control strategy and highlight the beneficial effects of indigenous QQ strains on AnMBR stability.

Degradation and decolourization potential of ligninolytic enzyme producing Bacillus paramycoides BL2 and Micrococcus luteus BL3 for pulp paper industrial effluent and its toxicity evaluation

Aim of this study was to optimize the production of Ligninolytic enzyme for the degradation of complex pollutants present in pulp paper industrial effluent (PPIE). Two ligninolytic enzyme-producing bacterial strains were isolated from PPIE and identified as Bacillus paramycoides strain BL2 (MZ676667) and Micrococcus luteus strains BL3 (MZ676668). The identified bacterial strain Bacillus paramycoides strain BL2 showed optimum production of LiP (4.30 U/ml), MnP (3.38 U/ml) at 72h of incubation, while laccase (4.43 U/ml) at 96h of incubation. While, Micrococcus luteusstrains BL3 produced maximum LiP (3.98) and MnP (3.85 U/ml) at 96h of incubation and maximum laccase (3.85 U/ml) at 72h of incubation, pH 7-8, and temperatures of 30-35°C. Furthermore, in the presence of glucose (1.0%) and peptone (0.5%) as nutrient sources, the enzyme activity of consortium leads to reduction of lignin (70%), colour (63%) along with COD (71%) and BOD (58%). The pollutants detected in control i.e. 3.6-Dioxa-2,7-disilaoctane, 2-Heptnoic acid,trimethylsilyl ester, 7-Methyldinaphtho [2,1-b,1',2'-d] silole, Hexadeconoic acid, trimethylysilyl ester, Methyl1(Z)-3,3-dipheny.1-4-hexenoale, 2,6,10,14,18,22-Tetracosahexane,2,2-dimethylpropyl(2Z,6E)-10,11epoxy5,6 Dihyrostigmasterol, acetate were completely diminished. The toxicity of PPIE was reduced up to 75%. Hence, knowledge of this study will be very useful for industrial sector for treatment of complex wastewater.

A synergistic arrangement of two unrelated IS elements facilitates adjacent deletion in Micrococcus luteus ATCC49732.

Mutants of Micrococcus luteus strain ATCC49732 lacking the yellow pigment sarcinaxanthin were observed at an unexpectedly high frequency and the molecular basis was investigated. PCR probing revealed complete deletion of the crt biosynthetic operon in 11/14 mutants. Inverse PCR was used to identify a common breakpoint 35kb downstream from crt precisely at the end of the right inverted repeat (IRR) of a partial ISMlu8 element that lies between two inversely oriented full-length ISMlu2. A total of three different breakpoints 5' to crt were found with the sequence CTAG one bp 5' to each novel junction. Analysis of 35 genomic sites with single ISMlu8 insertions showed that ISMlu8 transposase has high specificity for CTAG, implicating its key role in formation of the Δcrt deletions. No downstream deletion endpoints were observed at an immediately adjacent ISMlu8 with a nearly identical IRR in the same orientation and slightly closer to the crt operon, indicating that access of ISMlu8 transposase to the ISMlu2-flanked ISMlu8 IRR is greatly enhanced by the surrounding oppositely oriented ISMlu2s. The association of high frequency genomic rearrangement with this distinctive natural configuration of ISs from two different IS families offers a new insight into IS element evolutionary potential.

Micrococcus luteus strain CGK112 isolated from cow dung demonstrated efficient biofilm-forming ability and degradation potential toward high-density polyethylene (HDPE).

Biodegradation is the most promising environmentally sustainable method that offers a significant opportunity with minimal negative environmental consequences while searching for solutions to this global problem of plastic pollution that has now spread to almost everywhere in the entire world. In the present work, HDPE-degrading bacterial strain CGK112 was isolated from the fecal matter of a cow. The bacterial strain was identified as Micrococcus luteus CGK112 by 16S rRNA sequence coding analysis. Significant weight loss, i.e., 3.85% was recorded in the HDPE film treated with strain CGK112 for 90days. The surface micromorphology was examined using FE-SEM, which revealed spectacular bacterial colonization as well as structural deformation. Furthermore, the EDX study indicated a significant decrease in the atomic percentage of carbon content, whereas FTIR analysis confirmed functional groups alternation as well as an increase in the carbonyl index which can be attributed to the metabolic activity of biofilm. Our findings provide insight into the capacity of our strain CGK112 to colonize and utilize HDPE as a single carbon source, thus promoting its degradation.

Synergistic effect of phytohormone-producing ectomycorrhizal fungus Suillus luteus and fertilizer GGR6 on Pinus massoniana growth

ABSTRACT Suillus luteus is an edible ectomycorrhizal fungus (EMF). The S. luteus strain LS88 secretes many phytohormones, including salicylic acid (SA) and indole-3-carboxylic acid (ICA). LS88 was inoculated to the tree Pinus massoniana and treated with the amino acid fertilizer GGR6. Plant growth parameters, plant enzyme activities, chlorophyll contents, and element contents were analyzed. Our results show that GGR6 may help the development of S. luteus-P. massoniana ectomycorrhiza. Moreover, LS88 and GGR6 synergistically affect P. massoniana growth and element uptake. Phytohormone detection on the roots of LS88-inoculated P. massoniana seedlings showed that LS88 could significantly increase the ICA content within a week. The SA content in the roots in the inoculated group seedlings increased slightly, but the salicylic acid 2-O-β-glucoside (SAG) content decreased. Therefore, we speculate GGR6 may enhance the growth-promoting effect of EMF on plants, and LS88 affects P. massoniana growth through secreting phytohormones.

Rhizobacteria of Bali With Obvious Growth-Promoting Properties on Corn (Zea mays L.)

Corn productivity in Indonesia is still relatively low compared with other countries. Therefore, it is necessary to increase the productivity of corn by using rhizobacteria, which have multiple traits. This study was conducted to obtain indigenous rhizobacteria of Bali that have multiple traits, can produce indoleacetic acid (IAA), fix nitrogen from atmosphere, produce siderophores, colonize roots, increase seed germination, and promote the growth of corn. Isolation of rhizobacteria was carried out from the rhizosphere of plants belonging to the Gramineae family that grows in Bali Island, Indonesia. Six isolates, namely, Sr3, Tb9, Rg1, Rg23, Al27, and Jg8, could produce IAA, fix nitrogen from the atmosphere, produce siderophores, and increased germination rate and vigor index of corn seedling. Among them, three isolates, namely, Rg1, Sr3, and Jg8, significantly (p <0.05) increased the germination rate of corn seeds, increased vigor index, increased root dry weight and shoot dry weight of corn at the age of 7 days, and were able to colonize corn roots. Compared with the control, the rhizobacteria treatment increased the germination of corn seeds ranging from 5.04 to 13.05%. Based on the analysis of the 16S rRNA gene, it was found that these rhizobacteria species were Glutamicibacter nicotianae strain Rg1 (accession number OM349119), Brevibacillus invocatus strain Sr3 (accession number OM327515), and Micrococcus luteus strain Jg8 (accession number OM362349). Under a greenhouse condition, all the three isolates significantly (p <0.05) increased nutrient uptake, the leaf chlorophyll content, net assimilation rate, and crop growth rate of corn when compared with control. These results suggested that these isolates of rhizobacteria obviously promoted the growth of corn and can be developed as biostimulant to promote the growth and increase the corn yield in Bali, Indonesia.

Complete Genome Sequence of Micrococcus luteus Strain CW.Ay, Isolated from Indoor Air in a Hong Kong School.

ABSTRACTMicrococcus luteus strain CW.Ay was isolated from indoor air in Hong Kong. The complete genome (2,543,764 bp; GC content, 72.93%) was established by hybrid assembly and comprised a linear plasmid and a single chromosome featuring many genes to account for its broad distribution in very diverse habitats.

Changes in the number and intensity of sorption of Micrococcus luteus on carbon fiber at different degrees of its polarization

The electrogenic activity of many microorganisms used in MFC is due to direct electron transfer. It is achieved by direct contact of microbial cells with an electrode. In this regard, an important aspect of research in the field of MFC is the study of the interaction of electrogenic microorganisms with electrode materials. In this work, the influence of polarization of carbon fiber from an external source of electrical energy on the intensity of sorption on it of cells of the electrogenic strain Micrococcus luteus 1-i is considered. It was shown that the polarization of carbon fiber 0.6-0.8 V positively influenced the sorption of cells of the electrogenic strain M. luteus 1-i, and 0.4-0.6 V positively influenced the increase in the number of cells of the strain. The preliminary application of a voltage of 0.6 V to the MFC anode for 2 h led to an increase in the current generated by the M. luteus strain 1 within a 24hour experiment. The obtained positive effect demonstrates the possibility of using this approach to increase the efficiency of the MFC technology.

Plant Growth-promoting and Bio-control Activity of Micrococcus luteus Strain AKAD 3-5 Isolated from the Soybean (Glycine max (L.) Merr.) Rhizosphere

Background: Applications of bioinoculants for improving crop productivity may be an eco-friendly alternative to chemical fertilizers. Rhizosphere or soil-inhabiting beneficial microbes can enhance plant growth and productivity through direct and indirect mechanisms, i.e., phosphate solubilization, nutrient acquisition, phytohormone production, etc. Objective: This study is based on the hypothesis that diseases resistant plants can act as a source of potential microbes that can have good plant growth-promoting traits and bio-control potential. Methods: In this study, we have isolated the rhizobacterial strains (AKAD 2-1, AKAD 2-10, AKAD 3-5, AKAD 3-9) from the rhizosphere of a disease-resistant variety of soybean (JS-20-34) (Glycine max (L.) Merr.). These bacterial strains were further screened for various plant growth-promoting traits (phosphate solubilization, indole acetic acid (IAA), ammonia, biofilm, HCN, Exopolysaccharide (EPS), and enzyme production activity (catalase, cellulase, and chitinase)). Results: Among four, only bacterial strain AKAD 3-5 has shown plant-growth-promoting and biocontrol (98%) activity against Fusarium oxysporum. Morphological, biochemical, and molecular characterization (16S rRNA) revealed that this rhizobacterial isolate AKAD 3-5 closely resembles Micrococcus luteus (Gene bank accession: MH304279). Conclusion: Here, we conclude that this strain can be utilized to promote soybean growth under varied soil stress conditions.

Epinephrine affects gene expression levels and has a complex effect on biofilm formation in Micrococcus luteus strain C01 isolated from human skin

In this study, the effect of epinephrine on the biofilm formation of Micrococcus luteus C01 isolated from human skin was investigated in depth for the first time. This hormone has a complex effect on biofilms in various systems. In a system with polytetrafluoroethylene (PTFE) cubes, treatment with epinephrine at a physiological concentration of 4.9 × 10−9 M increased the total amount of 72-h biofilm biomass stained with crystal violet and increased the metabolic activity of biofilms, but at higher and lower concentrations, the treatment had no significant effect. On glass fiber filters, treatment with the hormone decreased the number of colony forming units (CFUs) and changed the aggregation but did not affect the metabolic activity of biofilm cells. In glass bottom plates examined by confocal microscopy, epinephrine notably inhibited the growth of biofilms. RNA-seq analysis and RT–PCR demonstrated reproducible upregulation of genes encoding Fe–S cluster assembly factors and cyanide detoxification sulfurtransferase, whereas genes encoding the co-chaperone GroES, the LysE superfamily of lysine exporters, short-chain alcohol dehydrogenase and the potential c-di-GMP phosphotransferase were downregulated. Our results suggest that epinephrine may stimulate matrix synthesis in M. luteus biofilms, thereby increasing the activity of NAD(H) oxidoreductases. Potential c-di-GMP pathway proteins are essential in these processes.

Clinical Characteristics of Patients with Micrococcus luteus Bloodstream Infection in a Chinese Tertiary-Care Hospital.

Few pieces of research have focused on Micrococcus luteus bloodstream infection (BSI) because of its low incidence; hence data is needed to illustrate this uncommon infection. This study aimed to explore the clinical characteristics of patients with M. luteus BSI. From January 2010 to December 2019, inpatients that met the criteria for M. luteus BSI were included in this study. Data was collected by reviewing electronic records. Ninety-seven patients were enrolled in this study. Sixty-three percent of the patients have a higher neutrophil percentage (NEUT%). The average blood C-reactive protein (CRP) concentration was 5.5 ± 6.4 mg/dl. 48.5% of the patients had malignancy, and 40.2% underwent invasive surgeries. Linezolid was found to have the largest average diameter of the inhibition zone (36 mm), while erythromycin was found to have the smallest average zone diameter (15 mm). However, some M. luteus strains had a potentially broad antimicrobial resistance spectrum. Cephalosporins (59.2%) and quinolones (21.4%) were the most commonly used antibiotics for empirical therapies. In conclusion, M. luteus BSI mainly happens in immunocompromised patients or those with former invasive surgeries or indwelling catheters. M. luteus strains are less responsive to erythromycin. Cephalosporins and quinolones are effective empirical antibiotics for M. luteus BSI; however, vancomycin and teicoplanin should be considered for potentially broadly drug-resistant M. luteus strains.

Comparative genomics reveals broad genetic diversity, extensive recombination and nascent ecological adaptation in Micrococcus luteus

BackgroundMicrococcus luteus is a group of actinobacteria that is widely used in biotechnology and is being thought as an emerging nosocomial pathogen. With one of the smallest genomes of free-living actinobacteria, it is found in a wide range of environments, but intraspecies genetic diversity and adaptation strategies to various environments remain unclear. Here, comparative genomics, phylogenomics, and genome-wide association studies were used to investigate the genomic diversity, evolutionary history, and the potential ecological differentiation of the species.ResultsHigh-quality genomes of 66 M. luteus strains were downloaded from the NCBI GenBank database and core and pan-genome analysis revealed a considerable intraspecies heterogeneity. Phylogenomic analysis, gene content comparison, and average nucleotide identity calculation consistently indicated that the species has diverged into three well-differentiated clades. Population structure analysis further suggested the existence of an unknown ancestor or the fourth, yet unsampled, clade. Reconstruction of gene gain/loss events along the evolutionary history revealed both early events that contributed to the inter-clade divergence and recent events leading to the intra-clade diversity. We also found convincing evidence that recombination has played a key role in the evolutionary process of the species, with upto two-thirds of the core genes having been affected by recombination. Furthermore, distribution of mammal-associated strains (including pathogens) on the phylogenetic tree suggested that the last common ancestor had a free-living lifestyle, and a few recently diverged lineages have developed a mammal-associated lifestyle separately. Consistently, genome-wide association analysis revealed that mammal-associated strains from different lineages shared genes functionally relevant to the host-associated lifestyle, indicating a recent ecological adaption to the new host-associated habitats.ConclusionsThese results revealed high intraspecies genomic diversity of M. luteus and highlighted that gene gain/loss events and extensive recombination events played key roles in the genome evolution. Our study also indicated that, as a free-living species, some lineages have recently developed or are developing a mammal-associated lifestyle. This study provides insights into the mechanisms that drive the genome evolution and adaption to various environments of a bacterial species.