[Mechanism of n-butanol alcohol extract of Baitouweng Decoction in treatment of vulvovaginal candidiasis based on negative regulation of NLRP3 inflammasome via PKCδ/NLRC4/IL-1Ra axis].

This study aimed to explore the mechanism of n-butanol alcohol extract of Baitouweng Decoction(BAEB) in the treatment of vulvovaginal candidiasis(VVC) in mice based on the negative regulation of NLRP3 inflammasome via PKCδ/NLRC4/IL-1Ra axis. In the experiment, female C57BL/6 mice were divided randomly into the following six groups: a blank control group, a VVC model group, high-, medium-, and low-dose BAEB groups(80, 40, and 20 mg·kg~(-1)), and a fluconazole group(20 mg·kg~(-1)). The VVC model was induced in mice except for those in the blank control group by the estrogen dependence method. After modeling, no treatment was carried out in the blank control group. The mice in the high-, medium-, and low-dose BAEB groups were treated with BAEB at 80, 40, and 20 mg·kg~(-1), respectively, and those in the fluconazole group were treated with fluconazole at 20 mg·kg~(-1). The mice in the VVC model group received the same volume of normal saline. The general state and body weight of mice in each group were observed every day, and the morphological changes of Candida albicans in the vaginal lavage of mice were examined by Gram staining. The fungal load in the vaginal lavage of mice was detected by microdilution assay. After the mice were killed, the degree of neutrophil infiltration in the vaginal lavage was detected by Papanicolaou staining. The content of inflammatory cytokines interleukin(IL)-1ß, IL-18, and lactate dehydrogenase(LDH) in the vaginal lavage was tested by enzyme-linked immunosorbent assay(ELISA), and vaginal histopathology was analyzed by hematoxylin-eosin(HE) staining. The expression and distribution of NLRP3, PKCδ, pNLRC4, and IL-1Ra in vaginal tissues were measured by immunohistochemistry(IHC), and the expression and distribution of pNLRC4 and IL-1Ra in vaginal tissues were detected by immunofluorescence(IF). The protein expression of NLRP3, PKCδ, pNLRC4, and IL-1Ra was detected by Western blot(WB), and the mRNA expression of NLRP3, PKCδ, pNLRC4, and IL-1Ra was detected by qRT-PCR. The results showed that compared with the blank control group, the VVC model group showed redness, edema, and white secretions in the vagina. Compared with the VVC model group, the BAEB groups showed improved general state of VVC mice. As revealed by Gram staining, Papanicolaou staining, microdilution assay, and HE staining, compared with the blank control group, the VVC model group showed a large number of hyphae, neutrophils infiltration, and increased fungal load in the vaginal lavage, destroyed vaginal mucosa, and infiltration of a large number of inflammatory cells. BAEB could reduce the transformation of C. albicans from yeast to hyphae. High-dose BAEB could significantly reduce neutrophil infiltration and fungal load. Low-and medium-dose BAEB could reduce the da-mage to the vaginal tissue, while high-dose BAEB could restore the damaged vaginal tissues to normal levels. ELISA results showed that the content of inflammatory cytokines IL-1ß, IL-18, and LDH in the VVC model group significantly increased compared with that in the blank control group, and the content of IL-1ß, IL-18 and LDH in the medium-and high-dose BAEB groups was significantly reduced compared with that in the VVC model group. WB and qRT-PCR results showed that compared with the blank control group, the VVC model group showed reduced protein and mRNA expression of PKCδ, pNLRC4, and IL-1Ra in vaginal tissues of mice and increased protein and mRNA expression of NLRP3. Compared with the VVC model group, the medium-and high-dose BAEB groups showed up-regulated protein and mRNA expression of PKCδ, pNLRC4, and IL-1Ra in vaginal tissues and inhibited protein and mRNA expression of NLRP3 in vaginal tissues. This study indicated that the therapeutic effect of BAEB on VVC mice was presumably related to the negative regulation of NLRP3 inflammasome by promoting PKCδ/NLRC4/IL-1Ra axis.

[Butyl alcohol extract of Baitouweng Decoction alleviates vulvovaginal candidiasis in mice by downregulating NLRP3 inflammasome and related signal pathways].

This study aims to explore the effect of butyl alcohol extract of Baitouweng Decoction(BAEB) on vulvovaginal candidiasis(VVC) in mice and to clarify the mechanism from Toll-like receptors(TLRs)/MyD88 and Dectin-1/Syk signal pathways and NLRP3 inflammasome. To be specific, female KM mice were randomized into control group(i.g., normal saline), model group, fluco-nazole group(i.g., 20 mg·kg~(-1)), and low-dose, medium-dose, and high-dose BAEB groups(i.g., 20, 40, and 80 mg·kg~(-1), respectively). VVC was induced in mice except the control group. After the modeling, administration began and lasted 7 days. The ge-neral conditions and body weight of mice were recorded every day. On the 1 st, 3 rd, 7 th, and 14 th after vaginal infection by Candida albicans, the fungal load in the vaginal lavage fluid of the mice was measured with the plate method, and the morphology of C. albicans in vaginal lavage fluid was observed based on Gram staining. After the mice were killed, vaginal tissues were subjected to hematoxylin-eosin(HE) staining and periodic acid-Schiff(PAS) staining for vaginal histopathological analysis. The content of cytokines in vaginal lavage fluid, such as interleukin(IL)-1ß, IL-18, tumor necrosis factor-α(TNF-α), IL-6, and S100 a8, was determined by enzyme-linked immunosorbent assay(ELISA), and content of reactive oxygen species(ROS) in vaginal tissues by tissue ROS detection kit. The protein expression of NLRP3, ASC, caspase-1, Dectin-1, Syk, MyD88, TLR2, TLR4, and nuclear factor-κB(NF-κB) in vaginal tissues was detected by Western blot, and the levels and distribution of NLRP3, Dectin-1, Syk, MyD88, TLR2, and TLR4 in vaginal tissues were determined with the immunohistochemical method. The results show that BAEB can improve the general conditions of VVC mice, reduce the fungal load and C. albicans hyphae in vaginal secretion, decrease ROS content in vaginal tissues and content of cytokines in vaginal lavage fluid, and down-regulate the expression of NLRP3, ASC, caspase-1, Dectin-1, Syk, MyD88, TLR2, TLR4, and NF-κB in vaginal tissues. The above results indicate that BAEB exerts therapeutic effect on VVC mice by down-regulating the key proteins in the TLRs/MyD88 and Dectin-1/Syk signal pathways and NLRP3 inflammasome.

[Effect of berberine hydrochloride on cell wall integrity of Candida albicans hypha].

The aim of this paper was to investigate the effect of berberine hydrochloride on the cell wall integrity of Candida albicans hypha. The minimal inhibitory concentration(MIC) of berberine hydrochloride against clinical and standard C. albicans strains was detected by micro liquid-based dilution method; the effect of berberine hydrochloride on the colony formation of C. albicans SC5314 was investigated by spot assay; the effect of berberine hydrochloride on the metabolism of C. albicans SC5314 hypha was checked by XTT reduction assay, and the viability of C. albicans SC5314 hypha was tested by fluorescent staining assay. The effect of berberine hydrochloride on the morphology of C. albicans SC5314 hypha was examined by scanning electron microscope. The changes in the cell wall of C. albicans SC5314 hypha after berberine hydrochloride treatment were detected by transmission electron microscopy. The effect of berberine hydrochloride on ß-glucan from C. albicans SC5314 was detected by flow cytometry. The effect of berberine hydrochloride on hypha-specific gene ECE1 and ß-glucan synthase genes FKS1 and FKS2 in C. albicans was examined by qRT-PCR. The results showed that berberine hydrochloride showed a strong inhibitory effect on both clinical and standard strains of C. albicans, and the MIC was 64-128 µg·mL~(-1). Spot assay, XTT redunction assay and fluorescent staining assay showed that with the increase of berberine hydrochloride concentration, the viability of C. albicans SC5314 gradually decreased. The transmission electron microscopy scanning assay showed that this compound could cause cell wall damage of C. albicans. The flow cytometry analysis showed the exposure degree of C. albicans ß-glucan. The qRT-PCR further showed that berberine hydrochloride could significantly down-regulate hypha-specific gene ECE1 and ß-glucan synthase-related gene FKS1 and FKS2. In conclusion, this compound can down-regulate C. albicans and ß-glucan synthase-related gene expressions, so as to destroy the cell wall structure of C. albicans, expose ß-glucan and damage the integrity of the wall.

[Therapeutic effect of cinnamaldehyde on ulcerative colitis in mice induced by dextran sulfate sodium with Candida albicans colonization and its effect on dectin-1/TLRs/NF-κB signaling pathway].

To observe the efficacy of cinnamaldehyde on dextran sulfate sodium(DSS)-induced ulcerative colitis(UC) with Can-dida albicans(Ca) colonization and its effect on dectin-1/TLRs/NF-κB signaling pathway in mice. C57 BL/6 mice were randomly divided into normal group, DSS group, DSS+Ca group, cinnamaldehyde group and mesalazine group. Mice in DSS+Ca group were given Ca(1×10~8 CFU per mouse) through intragastrical administration for 4 consecutive days and then distilled water with 3.0% DSS for 7 consecutive days. In cinnamaldehyde group and mesalazine group, in addition to the induction method of the DSS+Ca group, mice were given 75 mg·kg~(-1) cinnamaldehyde and 200 mg·kg~(-1) mesalazine accompanied with 3.0% DSS for 7 consecutive days, respectively. Mice in normal group and DSS group were correspondingly administered with distilled water. The general conditions of the mice were observed daily, the diseased activity index(DAI) score was calculated, and fungal loads of feces were detected by plate method. The mice were sacrificed on day 12, colon length was measured, colon mucosa damage index(CMDI) score was calculated, and histopathological analysis was carried out by HE staining. Anti-saccharomces cerevisiae antibody(ASCA) and ß-1,3-glucan in serum, and TNF-α, IL-1ß, IL-6, IL-8, IL-10 in serum and colon tissue were detected by ELISA. The contents of ß-1,3-glucan and macrophage infiltration in colon tissues were examined by immunofluorescence staining. The protein expressions of dectin-1, TLR2, TLR4 and NF-κB were detected by Western blot and immunohistochemistry staining. The results showed that cinnamaldehyde could significantly improve the general conditions of UC mice with Ca colonization, decrease DAI and histopathological scores, reduce intestinal mucosal congestion, erosion and colon shortening, decrease Ca load in mouse feces and tissues, down-regulate the contents of ASCA and ß-1,3-glucan in serum, reduce the contents of TNF-α, IL-1ß, IL-6, IL-8 and increase IL-10 in serum and colon tissues, inhibit macrophages infiltration and down-regulate the protein expression of dectin-1, TLR2, TLR4 and NF-κB in colon tissue. These results suggested that cinnamaldehyde had a therapeutic effect on UC mice with Ca colonization, which might be related to the inhibition of Ca proliferation, the regulation of dectin-1/TLRs/NF-κB signaling pathways and the coordination of the balance between pro-inflammatory and anti-inflammatory factors.

[Mechanism of butyl alcohol extract of Baitouweng Decoction (BAEB) on Candida albicans biofilms based on pH signal pathway].

This study aimed to investigate the effect of butyl alcohol extract of Baitouweng Decoction( BAEB) on Candida albicans biofilms based on pH signal pathway. The morphology of biofilms of the pH mutants was observed by scanning electron microscope. The biofilm thickness of the pH mutants was measured by CLSM. The biofilm activity of the pH mutants was analyzed by microplate reader.The biofilm damage of the pH mutants was detected by flow cytometry. The expression of pH mutant biofilm-related genes was detected by qRT-PCR. The results showed that the deletion of PHR1 gene resulted in the defect of biofilm,but there were more substrates for PHR1 complementation. BAEB had no significant effect on the two strains. RIM101 gene deletion or complementation did not cause significant structural damage,but after BAEB treatment,the biofilms of both strains were significantly inhibited. For the biofilm thickness,PHR1 deletion or complementation caused the thickness to decrease,after BAEB treatment,the thickness of the two strains did not change significantly. However,RIM101 gene deletion or complementation had little effect on the thickness,and the thickness of the two strains became thinner after adding BAEB. For biofilm activity,PHR1 deletion or complementation and RIM101 deletion resulted in decreased activity,RIM101 complementation did not change significantly; BAEB significantly inhibited biofilm activity of PHR1 deletion,PHR1 complemetation,RIM101 deletion and RIM101 complemetation strains. For the biofilm damage,PHR1 gene deletion or complementation,RIM101 gene deletion or complementation all showed different degrees of damage; after adding BAEB,the damage rate of PHR1 deletion or complementation was not significantly different,but the damage rate of RIM101 deletion or complementation was significantly increased. Except to the up-regulation of HSP90 gene expression,ALS3,SUN41,HWP1,UME6 and PGA10 genes of PHR1 deletion,PHR1 complementation,RIM101 deletion,and RIM101 complementation strains showed a downward expression trend. In a word,this study showed that mutations in PHR1 and RIM101 genes in the pH signaling pathway could enhance the sensitivity of the strains to the antifungal drug BAEB,thus inhibiting the biofilm formation and related genes expression in C. albicans.

[Inhibitory effect of extract of Coptidis Rhizoma on invasion of Candida albicans hyphae in vitro].

The aim of this paper was to investigate the inhibitory effect of extract of Coptidis Rhizoma(ECR) on invasion of Candida albicans hyphae in vitro.XTT reduction method was used to evaluate the metabolic activity of C.albicans.The colony edge growth of C.albicans was observed by solid medium.The growth of C.albicans hyphae was determined on semi-solid medium.The morphology and viability changes of C.albicans hyphae were assessed by scanning electron microscope and fluorescence microscope.qRT-PCR method was used to detect the ALS3 and SSA1 expression of C.albicans invasin genes.The results showed that the metabolic viability by XTT method detected that the activity of C.albicans was gradually decreased under the intervention of 64,128 and 256 mg·L-1 of ECR respectively.128,256 mg·L-1 of ECR significantly inhibited colony folds and wrinkles on solid medium and the hyphal invasion in semi-solid medium.Scanning electron microscopy and fluorescence microscopy showed that 128,256 mg·L-1 of ECR could inhibit the formation of C.albicans hyphae.qRT-PCR results showed that the expression of invasin gene ALS3 and SSA1 was down-regulated,and especially 256 mg·L-1 of ECR could down-regulate the two genes expression by 4.8,1.68 times respectively.This study showed that ECR can affect the invasiveness of C.albicans by inhibiting the growth of hyphae and the expression of invasin.

[Therapeutic potential of n-butanol extract of Pulsatilla decoction in a murine model of ulcerative colitis induced by DSS combined with Candida albicans colonization].

To investigate the mechanism of n-butanol extract of Pulsatilla decoction (BAEB) against murine ulcerative colitis (UC) model induced by DSS combined with Candida albicans (CA) colonization, mice were randomly divided into normal control group, DSS group, DSS+CA group, BAEB high, medium and low dose group, and positive drug Mesalazine group. The general condition of mice was observed, fungal loads of murine intestinal contents were detected by plate method, colonic pathological change of mice was examined by HE staining. ASCA in serum and IL-6, IL-8, IL-1ß, HBD-2, HBD-3 in colonic mucosa were detected by ELISA. The results showed that, compared with DSS group, the general condition and ASCA in serum had no obvious change for DSS+CA group, but the fungal loads in intestinal contents, the colonic pathological damage, and the levels of IL-6, IL-8, IL-1ß, HBD-2, HBD-3 in colonic mucosa were greater than that of DSS group. High dose of BAEB group and Mesalazine group could improve the colonic pathology, decrease IL-6, IL-8, IL-1ß, HBD-2, HBD-3 expression level. In conclusion, BAEB could effectively improve the UC symptoms in mice induced by DSS combined with CA colonization, and inhibit the inflammatory factors such as IL-6, imply that BAEB is of important value for the treatment of intestinal fungal-related colitis.

[Effect of chloroform extracts from Longdan Xiegan decoction in inhibiting hydrolytic enzyme activity of Candida albicans isolated from VVC patients].

To investigate the inhibitory effect and mechanism of chloroform extracts from Longdan Xiegan decoction(CELX) against hydrolytic enzymes activity of Candida albicans isolated from vulvovaginal candidiasis(VVC) patients. Secreted aspartyl proteinase(Sap), phospholipase(PL) and lipase(Lip) positive strains were identified from 15 strains of C. albicans with milk culture medium, egg yolk culture medium and tween-80 medium, respectively. Then, the activities of Sap, PL, and Lip were detected in the above media. qRT-PCR was used to detect the changes in gene expressions of aspartic protease(SAP1-7,10), phospholipase B(PLB1-2) and lipase(LIP3-6). Secreted aspartyl proteinase and phospholipase of 15 VVC clinical strains were positive, and lipase of 11 strains were positive. Compared with the blank control group, the drug CELX-containing medium(milk medium, egg yolk culture medium, tween-80 medium) experiment showed that the sedimentation of colonies decreased gradually in each culture medium with the increase of CELX dose. When the concentration of CELX was 256 mg•L⁻¹, the colony almost disappeared, which indicated the enzyme activity was significantly weakened. The results of qRT-PCR showed that SAP1, SAP2, SAP3, SAP4, SAP7, SAP9 and SAP10 were down-regulated by 62%, 55%, 62%, 84%, 61%, 51%, 68%, respectively, except for SAP5 and SAP6; and PLB1, LIP3, LIP4, LIP6 were down-regulated by 67%, 51%, 54%, 55%, respectively. The findings suggested that CELX may inhibit the activities of Sap, PL, and Lip, which are important virulence factors of C. albicans.

[Effect of sodium houttuyfonate in combination with erythromycin on luxS, agr/RNAâ ¢ of Staphylococus epidermidis].

Quorum sensing of bacteria and its specific gene expression regulation have a very important role in bacterial biofilm formation. LuxS and agr are the key regulatory genes in quorum sensing of Staphylococcus epidermidis, and RNA Ⅲ is the effector molecule of agr system. In order to evaluate the effects of sodium houttuyfonate in combination with erythromycin on the transcription level of S. epidermidis, serial dilution method was used to determine the MIC of sodium houttuyfonate, erythromycin and vancomycin on S. epidermidis, and fluorescent quantitative PCR method was used to detect the transcription levels of luxS, agr/RNAⅢ in different time periods after treatment on S. epidermidis by sodium houttuyfonate in combination with erythromycin, vancomycin, and erythromycin alone. Our results showed that in treatment by 1/2MIC, 1/4MIC sodium houttuyfonate, 1/2MIC sodium houttuyfonate +1/2MIC erythromycin, 1/4MIC sodium houttuyfonate+1/4MIC erythromycin, and 1/8MIC sodium houttuyfonate+1/8MIC erythromycin for ATCC 35984, they could rapidly up-regulate the expression of luxS of S. epidermidis from the beginning as compared with negative control, with significant differences (P<0.05); furthermore, sodium houttuyfonate can still up-regulate the expression of luxS even after treatment for 6, 12 and 48 h. Sodium houttuyfonate in MIC and 1/2MIC concentration can significantly down-regulate the expression of agr (P<0.05); 1/2MIC sodium houttuyfonate+1/2MIC erythromycin, 1/4MIC sodium houttuyfonate+1/4MIC erythromycin, can also significantly down-regulate the expression of agr in 6 h, 12 h and 24 h(P<0.05). Sodium houttuyfonate in MIC, can significantly down-regulate the expression of RNA Ⅲ (P<0.05), and 1/2MIC sodium houttuyfonate+1/2MIC erythromycin can also significantly down-regulate the expression of RNAⅢ(P<0.05). Therefore, our presented results showed that sodium houttuyfonate in combination with erythromycin can rapidly up-regulate the transcription of luxS of S. epidermidis, and can down-regulate the expression of agr/RNA Ⅲ in certain concentrations, and suggested that sodium houttuyfonate in combination of erythromycin could inhibit mutual aggregation between S. epidermidis and biofilm bacteria, inhibit membrane nutrition and formation of water transport channels, prevent separation of bacterial cells in biofilm, and inhibit the formation of bacterial exotoxin of S. epidermidis.

Sodium houttuyfonate inhibits biofilm formation and alginate biosynthesis-associated gene expression in a clinical strain of Pseudomonas aeruginosa in vitro.

The increasing multidrug resistance of Pseudomonas aeruginosa has become a serious public-health problem. In the present study, the inhibitory activities of sodium houttuyfonate (SH) against biofilm formation and alginate production in a clinical strain of P.aeruginosa (AH16) were investigated in vitro using crystal violet dying and standard curve methods, respectively. The cellular morphology of P. aeruginosa treated with SH was observed using a scanning electron microscope. Furthermore, reverse transcription-quantitative polymerase chain reaction was used to identify differences in the expression levels of genes associated with alginate biosynthesis as a result of the SH treatment. The results indicated that SH significantly inhibited biofilm formation, and decreased the levels of the primary biofilm constituent, alginate, in P. aeruginosa AH16 at various stages of biofilm development. In addition, scanning electron microscopy observations demonstrated that SH markedly altered the cellular morphology and biofilm structure of P. aeruginosa. Furthermore, the results from the reverse transcription-quantitative polymerase chain reaction analysis indicated that SH inhibited biofilm formation by mitigating the expression of the algD and algR genes, which are associated with alginate biosynthesis. Therefore, the present study has provided novel insights into the potent effects and underlying mechanisms of SH-induced inhibition of biofilm formation in a clinical strain of P. aeruginosa.

[Sodium houttuyfonate inhibits virulence related motility of Pseudomonas aeruginosa].

Sodium houttuyfonate (SH) is a derivative of effective component of a Chinese material medica, Houttuynia cordata, which is applied in anti-infection of microorganism. But, the antimicrobial mechanisms of SH still remain unclear. Here, we firstly discovered that SH effectively inhibits the three types of virulence related motility of.Pseudomonas aeruginosa, i.e., swimming, twitching and swarming. The plate assay results showed that the inhibitory action of SH against swimming and twitching in 24 h and swarming in 48 h is dose-dependent; and bacteria nearly lost all of the motile activities under the concentration of 1 x minimum inhibitory concentration (MIC) (512 mg x L(-1) same as azithromycin positive group (1 x MIC, 16 mg x L(-1)). Furthermore, we found that the expression of structural gene flgB and pilG is down-regulated by SH, which implies that inhibitory mechanism of SH against motility of P. aeruginosa may be due to the inhibition of flagella and pili bioformation of P. aeruginosa by SR Therefore, our presented results firstly demonstrate that SH effectively inhibits the motility activities of P. aeruginosa, and suggest that SH could be a promising antipseudomonas agents in clinic.

Transcriptome analysis of candidate genes and signaling pathways associated with light-induced brown film formation in Lentinula edodes.

High-throughput Illumina RNA-seq was used for deep sequencing analysis of the transcriptome of poly(A)+ RNA from mycelium grown under three different conditions: 30 days darkness (sample 118), 80 days darkness (313W), and 30 days darkness followed by 50 days in the light (313C), in order to gain insight into the molecular mechanisms underlying the process of light-induced brown film (BF) formation in the edible mushroom, Lentinula edodes. Of the three growth conditions, BF formation occurred in 313C samples only. Approximately 159.23 million reads were obtained, trimmed, and de novo assembled into 31,511 contigs with an average length of 1,746 bp and an N 50 of 2,480 bp. Based on sequence orientations determined by a BLASTX search against the NR, Swiss-Prot, COG, and KEGG databases, 24,246 (76.9 %) contigs were assigned putative descriptions. Comparison of 313C/118 and 313C/313W expression profiles revealed 3,958 and 5,651 significantly differentially expressed contigs (DECs), respectively. Annotation using the COG database revealed that candidate genes for light-induced BF formation encoded proteins linked to light reception (e.g., WC-1, WC-2, phytochrome), light signal transduction pathways (e.g., two-component phosphorelay system, mitogen-activated protein kinase pathway), and pigment formation (e.g., polyketide synthase, O-methyltransferase, laccase, P450 monooxygenase, oxidoreductase). Several DECs were validated using quantitative real-time polymerase chain reaction. Our report is the first to identify genes associated with light-induced BF formation in L. edodes and represents a valuable resource for future genomic studies on this commercially important mushroom.

Genome sequence of Pseudomonas aeruginosa strain AH16, isolated from a patient with chronic pneumonia in China.

Pseudomonas aeruginosa AH16 is a virulent strain isolated from a patient with chronic pneumonia in China. Here, we present a 6.8-Mb (G+C content, 66.13%) assembly of its genome with 6,332 putative coding sequences, which may provide insights into the genomic basis of activity of the clinical P. aeruginosa strain in China.

Comparative analysis of temperature-dependent transcriptome of Pseudomonas aeruginosa strains from rhizosphere and human habitats.

In this study, we investigated the effects of a change in growth temperature on the transcriptome of two strains of Pseudomonas aeruginosa. The chosen P. aeruginosa strains were M18 and PAO1, which are adapted to two different niches, rhizosphere and human, respectively. To assess the changes induced by a change in temperature, we used a newly designed microarray covering the complete genome of four P. aeruginosa strains: PAO1, M18, PA14 and LESB58, which proved informative and reliable for the transcriptome study. Using the microarray, we analysed the transcriptome profile changes of two P. aeruginosa strains of M18 and PAO1 at their originating and non-originating temperatures: 28 °C for the rhizosphere and 37 °C for the human. The transcriptome profiles showed significant temperature-dependent differences (64.8 % in M18 and 66.8 % in PAO1) compared with the genome structure (6 % in M18 and 4.1 % in PAO1). Furthermore, we found that the specific induced genes at the non-originating growth temperature of the each strain (207 genes in M18 and 229 genes in PAO1) were evidently more than those induced at the originating growth temperature (158 genes in M18 and 169 genes in PAO1). The functional analysis of several newly found specific regulated operons (such as phh, liu, hmg) in the two strains indicated possible strategies implemented to respond to the non-originating temperature. This study provides new insight into how P. aeruginosa species responds to temperature change and a microarray platform covering the complete genomes of four widely studied P. aeruginosa strains.

Genomic analysis and temperature-dependent transcriptome profiles of the rhizosphere originating strain Pseudomonas aeruginosa M18.

BACKGROUND: Our previously published reports have described an effective biocontrol agent named Pseudomonas sp. M18 as its 16S rDNA sequence and several regulator genes share homologous sequences with those of P. aeruginosa, but there are several unusual phenotypic features. This study aims to explore its strain specific genomic features and gene expression patterns at different temperatures. RESULTS: The complete M18 genome is composed of a single chromosome of 6,327,754 base pairs containing 5684 open reading frames. Seven genomic islands, including two novel prophages and five specific non-phage islands were identified besides the conserved P. aeruginosa core genome. Each prophage contains a putative chitinase coding gene, and the prophage II contains a capB gene encoding a putative cold stress protein. The non-phage genomic islands contain genes responsible for pyoluteorin biosynthesis, environmental substance degradation and type I and III restriction-modification systems. Compared with other P. aeruginosa strains, the fewest number (3) of insertion sequences and the most number (3) of clustered regularly interspaced short palindromic repeats in M18 genome may contribute to the relative genome stability. Although the M18 genome is most closely related to that of P. aeruginosa strain LESB58, the strain M18 is more susceptible to several antimicrobial agents and easier to be erased in a mouse acute lung infection model than the strain LESB58. The whole M18 transcriptomic analysis indicated that 10.6% of the expressed genes are temperature-dependent, with 22 genes up-regulated at 28°C in three non-phage genomic islands and one prophage but none at 37°C. CONCLUSIONS: The P. aeruginosa strain M18 has evolved its specific genomic structures and temperature dependent expression patterns to meet the requirement of its fitness and competitiveness under selective pressures imposed on the strain in rhizosphere niche.