Future Microbiol 2007, 2:605–618.CrossRefPubMed 23. Bycroft BW, Maslen C, Box SJ, Brown A, Tyler JW: The biosynthetic implications of acetate and glutamate incorporation into (3R,5R)-carbapenam-3-carboxylic acid and (5R)-carbapen-2-em-3-carboxylic acid by Serratia sp. J Antibiot (Tokyo) 1988,41(9):1231–1242. 24. Parker WL, Rathnum ML, Wells JS Jr, Trejo WH, Principe

PA, Sykes RB: SQ 27,860, a simple carbapenem produced by species of Serratia and Erwinia. J Antibiot (Tokyo) 1982,35(6):653–660. 25. Thomson NR, Crow MA, McGowan SJ, Cox A, Salmond GP: Biosynthesis of carbapenem antibiotic and prodigiosin pigment in Serratia is under quorum sensing control. Mol Microbiol 2000,36(3):539–556.CrossRefPubMed 26. Williamson NR, Simonsen selleck chemicals llc HT, Y-27632 concentration Ahmed RA, Goldet G, Slater H, Woodley L, Leeper FJ, Salmond GP: Biosynthesis of the red antibiotic, prodigiosin, in Serratia : identification of a novel 2-methyl-3-n-amyl-pyrrole (MAP) assembly pathway, definition of the terminal condensing enzyme, and implications for undecylprodigiosin biosynthesis in Streptomyces. Mol Microbiol 2005,56(4):971–989.CrossRefPubMed 27. Williamson NR, Fineran PC, Leeper FJ, Salmond GP: The biosynthesis and regulation of bacterial prodiginines. Nat Rev Microbiol

2006,4(12):887–899.CrossRefPubMed 28. Fineran PC, Slater H, Everson L, Hughes K, Salmond GP: Biosynthesis of tripyrrole and beta-lactam secondary metabolites in Serratia : integration of quorum sensing with multiple new regulatory components in the control of prodigiosin and carbapenem antibiotic production. Mol Microbiol 2005,56(6):1495–1517.CrossRefPubMed 29. Slater H, Crow M, Everson L, Salmond GP: Phosphate availability regulates biosynthesis of two antibiotics, Aspartate prodigiosin and carbapenem, in Serratia via both quorum-sensing-dependent and -independent pathways. Mol Microbiol 2003,47(2):303–320.CrossRefPubMed 30. Van Houdt R, Givskov M, Michiels CW: Quorum sensing in Serratia. FEMS Microbiol Rev 2007,31(4):407–424.CrossRefPubMed 31. Thomson NR, Cox A, Bycroft BW, Stewart GS, Williams P, Salmond GP: The rap and hor

proteins of Erwinia, Serratia and Yersinia : a novel subgroup in a growing superfamily of proteins regulating diverse physiological processes in bacterial pathogens. Mol Microbiol 1997,26(3):531–544.CrossRefPubMed 32. Cathelyn JS, Crosby SD, Lathem WW, Goldman WE, Miller VL: RovA, a global regulator of Yersinia pestis , specifically required for bubonic plague. Proc Natl Acad Sci USA 2006,103(36):13514–13519.CrossRefPubMed 33. Ellison DW, Lawrenz MB, Miller VL: Invasin and beyond: regulation of Yersinia virulence by RovA. Trends Microbiol 2004,12(6):296–300.CrossRefPubMed 34. Nagel G, Lahrz A, Dersch P: Environmental control of invasin expression in Yersinia pseudotuberculosis is mediated by regulation of RovA, a transcriptional see more activator of the SlyA/Hor family. Mol Microbiol 2001,41(6):1249–1269.CrossRefPubMed 35.

(1998), implemented in the software MolKin 2.0 (Gutiérrez et al. 2005). Briefly, for each sample we estimated (1) within-sample diversity measured as allelic richness of the sample relative to the allelic richness of the other samples of the same species, and (2) genetic differentiation of the sample in relation to the other samples of the same species using a measure related to Nei’s D ST and G ST (Gutiérrez Inflammation related inhibitor et al. 2005). Positive values of relative diversity and/or differentiation for a particular sampled region indicate that the sample of that region contributes positively to total genetic diversity of the global

Baltic population. Negative values correspondingly indicate that the relative diversity or divergence of the sample in question is low

and does not contribute to total genetic diversity (Petit et al. 1998). The values for relative diversity and differentiation were used to categorize each sample into one of four categories, as identified by Swatdipong et al. (2009) including (i) higher diversity-higher divergence, (ii) higher diversity-lower divergence, (iii) lower diversity-higher divergence, and (iv) lower diversity-lower divergence. Samples in each category can be selleckchem expected to be characterized by the differing roles of migration Omipalisib supplier and genetic drift affecting the genetics of populations. Categories i and ii are considered to have the largest potential of containing unique genetic material and should potentially be prioritized in conservation (Swatdipong

et al. 2009). The observed strong divergence of Baltic populations from Atlantic conspecifics (Johannesson and André 2006) prompted the exclusion of Atlantic samples from these analyses to amplify the diversity-divergence classification within the Baltic Sea. The difference enough in the distribution of observed frequencies of the four diversity-divergence categories in different geographic regions relative to the expected frequencies under the null hypothesis of random distribution of diversity-divergence was tested with a χ 2 test for independence. Areas of genetic discontinuities We used the software Barrier 2.2 (Manni et al. 2004) to locate areas of major genetic discontinuities. Barrier applies Monmonier’s algorithm to detect the areas of highest genetic change on a map (genetic barriers) where the samples are represented by their geographic coordinates and connected by Delauney triangulation. The software produces as many barriers as the user defines, regardless of how strong these barriers are, i.e. if they are supported by significant F ST values or not. For example in the case of the Atlantic herring in this study, there is no significant differentiation among populations within the Baltic Sea, but Barrier still identifies genetic breaks if asked to do so.

CrossRef 2. Colombo AL, Nucci M, Park BJ, Noue’R SA, Arthington-Skaggs B, Matta DA, Warnock D, Morgan J: Epidemiology of candidemia in Brazil: a nationwide sentinel surveillance of candidemia in eleven medical centers. J Clin Microbiol 2006, 44:2816–2823.CrossRefPubMed

#GSK458 in vivo randurls[1|1|,|CHEM1|]# 3. Pappas PG, Rex JH, Sobel JD, Filler SG, Dismukes WE, Walsh TJ, Edwards JE: Guidelines of treatment of candidiasis. Clin Infect Dis 2004, 38:161–189.CrossRefPubMed 4. Odds FC, Brown AJ, Gow NA: Antifungal agents: Mechanism of action. Trends Microbiol 2003, 11:272–279.CrossRefPubMed 5. Pasqualotto AC, Denning DW: New and emerging treatments for fungal infections. J Antimicrob Chemother 2008,61(Suppl 1):i19-i30.CrossRefPubMed 6. Barret-Bee K, Ryder NS: Biochemical aspects of ergosterol biosynthesis inhibition. Emerging targets in antibacterial and antifungal chemotherapy (Edited by: Sutcliffe J, Georgopapadakou NH). New York: Chapman & Hall 1992, 410–436. 7. Burbiel J, Bracher F: Azasteroids as

antifungals. Steroids 2003, 68:587–594.CrossRefPubMed 8. Oehlschlager AC, Czyzewska E: Rationally designed inhibitors of sterol biosynthesis. Emerging targets in antibacterial and antifungal chemotherapy (Edited by: Sutcliffe J, Georgopapadakou NH). New York: Chapman & Hall 1992, 437–475. 9. Song Z, Nes WD: Sterol biosynthesis inhibitors: Potential for transition state analogs and mechanism-based inactivators targeted at sterol methyltransferase. Lipids 2007, 42:15–33.CrossRefPubMed 10. Urbina JA, Vivas J, Visbal G, Contreras LM: Modification of the composition of Trypanosoma selleck kinase inhibitor (Schizotrypanum)

cruzi epimastigotes by Δ 24(25) sterol methyltransferase inhibitors and their combinations with ketoconazole. Mol Biochem Parasitol 1995, Thiamine-diphosphate kinase 73:199–210.CrossRefPubMed 11. Rodrigues JCF, Bernardes CF, Visbal G, Urbina JA, Vercesi AE, de Souza W: Sterol methenyl transferase inhibitors alter the ultrastructure and function of the Leishmania amazonensis mitochondrion leading to potent growth inhibition. Protist 2007, 158:447–456.CrossRefPubMed 12. Rodrigues JCF, Attias M, Rodriguez C, Urbina JA, de Souza W: Ultrastructural and biochemical alterations induced by 22,26-azasterol, a Δ 24(25) -sterol methyltransferase inhibitor, on promastigote and amastigote forms of Leishmania amazonensis. Antimicrob Agents Chemother 2002, 46:487–499.CrossRefPubMed 13. Urbina JA, Visbal G, Contreras LM, Mclaughlin G, Docampo R: Inhibitors of D24(25) sterol methyltransferase block sterol synthesis and cell proliferation in Pneumocystis carinii. Antimicrob Agents Chemother 1997, 41:1428–1432.PubMed 14. Visbal G, Alvarez A, Moreno B, San-Blas G:S -adenosyl-L-methionine inhibitors Δ24-sterol methyltransferase and Δ24(28)-sterol methylreductase as possible agents against Paracoccidioides brasiliensis. Antimicrob Agents Chemother 2003, 47:2966–2970.CrossRefPubMed 15. Borg-von Zepelin M, Kunz L, Rüchel R, Reichard U, Weig M, Groß U: Epidemiology and antifungal susceptibilities of Candida spp.

A repeat fluoroscopic contrast study of the drain showed resolution of the abscess GDC-0449 price and fistula. The drain was then removed without complication. Three months following drain removal, the patient was noted to be tolerating a regular diet with no signs of infection or fistula drainage. She suffered only mild deconditioning and had no significant loss of functional status. Figure 4 CT image of collapsed abscess cavity. CT image of the pelvis without contrast shows the drain in place and the abscess cavity completely collapsed. Discussion Migration of endoscopically placed biliary stents is a well recognized complication of ERCP. Less than 1% of migrated

stents cause intestinal perforation.[5] Of those that do perforate the bowel, the vast majority occur proximal to the ligament of Trietz (LOT). There have been a several case reports of intestinal perforation distal to the LOT, generally in the colon. [6–9] There have also been case reports describing small bowel perforation. [10–13] Generally speaking, a double pigtail stent (7F) is preferable in cases involving choledocholithiasis. A straight stent may migrate since there is nothing to hold it in place, even though there are side flaps. An exception might be an impacted stone that is tight on the stent and prevents migration. Dislodged straight stents are more likely to perforate

bowel whereas perforation with a pigtail is much more rare. Furthermore, straight 10 F plastic stents should generally be used for conditions such as strictures and tumours. The rationale IWP-2 mouse for a double pigtail stent (7F) in this case is not known to the authors. Migrated stents causing complications have either been retrieved endoscopically or via laparotomy.[4, 7, 14] There is at least one documented case of a percutaneous intervention to remove a biliary stent causing a selleck chemicals retroperitoneal duodenal perforation and bilioma. However, there has not been a documented case involving percutaneous methods to retrieve a migrated stent beyond the LOT. The

existing literature on this subject would advocate prompt and aggressive surgical intervention because of gross contamination, intraperitoneal abscess, Astemizole and bowel perforation.[4, 5] Prompt surgical intervention is generally indicated for small bowel perforations, especially in the setting of a highly contaminated field, bowel obstruction and generalized abdominal pain. Historically, bowel perforation from migrated bilary stents has been treated either by endoscopic retrieval or laparotomy should endoscopic means fail. There are reports in which endoscopy is used to retrieve stents and close bowel perforations via clip application, but this only applies to areas that are accessible to endoscopic instrumentation.[14] In our case, endoscopic means was not possible because the perforation was in the distal small bowel and associated with a partial small bowel obstruction.

, while the GABRI method is more sensitive to the presence of Bacillus anthracis compared to the classic method. Epigenetics inhibitor Figure 1 Bland Altman difference plot indicating agreement between G.A.B.R.I and classic tests. The mean difference is −282.1 percentage points with 95% confidence interval −377.8 to −186.5 (Standard Deviation = 350.6). The limits of agreement are: Upper agreement limit = 419.1 (95% CI: 253.3 – 584.8 ) and Lower agreement limit = −983.3 (95% CI: -1149.1 – -817.6 ). To improve the efficiency of classical procedures for detection of anthrax spores in environmental samples, we evaluated a new

microbiologic method which in preliminary tests proved to be sensitive

and able to distinguish B. anthracis from other ubiquitous species. When environmental samples are tested for the presence of anthrax spores, the main problems are efficiently separating Bacillus spores from soil particles and strongly reducing the presence of contaminants AZD5582 concentration which being much more numerous than B. anthracis, tend to either inhibit the development of anthrax organisms or just make it extremely difficult to accurately read the cultured result. The contamination with vegetative cells is not a problem, since they can be easily eliminated by treating samples at temperatures that are lethal for vegetative microbes but not for spores. It has been demonstrated that Bacillus spores are hydrophobic and that they adhere to solid matrices especially by mean of hydrophobic interactions [19]. In the GABRI method soil samples were washed for a long time (30 min) with a wash buffer containing 0.5% of Tween 20. As previously demonstrated, in fact, MRIP the non-ionic detergents, such as Triton or Tween, allow the separation of spores from soil particles by disrupting hydrophobic interactions with solid matrices [9]. After washing with Tween 20, anthrax spores were recovered

from supernatant by centrifugation. To reduce the presence of contaminants, we treated soil samples with fosfomycin. To evaluate the environmental behavior of B. anthracis, Schuch and Fischetti investigated on the role of bacteriophages on bacterial adaptive behavior and niche expansion. In their study, the phage proteins encoding for fosfomycin resistance were specifically described in the spore surface structure of B. anthracis. Genes encoding surface proteins and antibiotic resistance may not be virulence factors in the classic sense but can help B. anthracis better survive within the highly competitive soil environment [20]. Based on these findings, in the GABRI method supernatants of soil samples, containing anthrax spores, were incubated with fosfomycin (50 μg/μl ) prior to being learn more plated onto selective medium.

marcescens BMN 673 mouse strain 12 (67% identity), SmaI (CAB92553) from Serratia strain ATCC 39006 (60% identity). The AHL synthases SwrI and SmaI catalyze preferentially the synthesis of C4-HSL and, in less amount, C6-HSL [16, 37, 38]. To examine the evolutionary relationship between the LuxI family members described above, a phylogenetic analysis was performed using MEGA 4 and the neighbour-joining tree was showed in Figure 1. The results were consistent with the similarity analysis of amino acid sequences within LuxI family members, the LuxI family synthases were clustered into two groups, and SplI and SpsI from strain G3 are classified into group A and group B, respectively. Figure

1 Neighbour-joining tree of LuxI family members in Serratia. The phylogenetic tree was see more generated using MEGA 4. LuxI family members in Serratia are clustered into two groups according to the AHL patterns. SplI and SpsI from G3 were in group A and group B, respectively. The significance of each branch is bootstrap value calculated for 1000 subsets. Scale bar indicates the mean number of substitutions per site. SplI and SpsI from S. plymuthica G3 produce multiple AHLs To determine which AHLs were made by each SplI and SpsI, LC-MS/MS analysis was performed on extracted culture supernatants from the wild type G3 strain click here as well as recombinant E. coli strains expressing splI or spsI and the spectra

profiles compared to that of synthetic AHL standards. At least ten different AHLs were detected in varying abundance in the wild type G3, including unsubstituted AHLs (C4-HSL, C5-HSL, C6-HSL, C7-HSL, C8-HSL), 3-oxo derivatives (3-oxo-C6-HSL, 3-oxo-C7-HSL, 3-oxo-C8-HSL) and 3-hydroxy derivatives (3-hydroxy-C6-HSL, 3-hydroxy-C8-HSL). The most abundant and hence most likely biologically relevant AHLs detected in the spent culture supernatants of the endophytic strain G3 were 3-oxo-C6-HSL, C4-HSL, C6-HSL, 3-hydroxy-C6-HSL and 3-oxo-C7-HSL. However, strain G3 did not produce long chain AHLs [23]. When expressed in E. coli (Table 2),

the recombinant SplI produced all ten Mirabegron AHLs whereas SpsI produced only unsubstituted AHLs, including C4-HSL, C5-HSL, C6-HSL, C7-HSL, and C8-HSL. The most abundant one was C4-HSL from SpsI, 100 fold higher than that the production of this molecule by SplI in E. coli, suggesting that SpsI is could also be the main AHL synthase responsible for synthesis of this AHL in G3, in accordance with SwrI and SmaI from different S. marcescens strains [37, 38] which share similarity to SpsI. Both SpsI and SplI produce C6-HSL, but only SplI was responsible for the most abundant signal 3-oxo-C6-HSL, that is similar to SplI from S. plymuthica strains HRO-C48 and RVH1 [14, 32], SprI from S. proteamaculans B5a, SpnI from S. marcescens SS-1 [34, 35], as well as EsaI from P. stewartii [36].

PubMedCrossRef 9. Qiu D, Eisinger VM, Rowen DW, Yu HD: Regulated proteolysis controls mucoid conversion in Pseudomonas aeruginosa . Proc Natl Acad Sci U S A 2007,104(19):8107–8112.PubMedCrossRef 10. Lizewski SE, Schurr JR, Jackson DW, Frisk A, Carterson AJ, Schurr MJ: Identification

of AlgR-regulated genes in Pseudomonas aeruginosa by use of microarray analysis. J Bacteriol 2004,186(17):5672–5684.PubMedCrossRef 11. Figurski DH, Helinski DR: Replication of an origin-containing derivative of plasmid RK2 dependent on a plasmid function provided in trans. Proc Natl Acad Sci U S A 1979,76(4):1648–1652.PubMedCrossRef 12. Hoang TT, Kutchma AJ, Becher A, Schweizer HP: Integration-proficient plasmids for Pseudomonas aeruginosa : site-specific integration eFT-508 solubility dmso and use for engineering of reporter and expression strains. Plasmid 2000,43(1):59–72.PubMedCrossRef selleck 13. Miller JH: Beta-Galactosidase Assay. In Experiments in Molecular Genetics. Edited by: Miller JH. Cold Spring Harbor, New York: Cold Spring Harbor Laboratory; 1972:352–355. 14. Damron FH, Qiu D, Yu HD: The Pseudomonas aeruginosa sensor kinase KinB negatively controls alginate production through AlgW-dependent MucA proteolysis. J Bacteriol 2009,191(7):2285–2295.PubMedCrossRef 15. Damron FH, Owings JP, Okkotsu Y, Varga JJ, Schurr

JR, Goldberg JB, Schurr MJ, Yu HD: Analysis of the Pseudomonas aeruginosa regulon controlled by the sensor kinase KinB and sigma factor RpoN. J Bacteriol 2012,194(6):1317–1330.PubMedCrossRef 16. Qiu D, Damron FH, Mima T, Schweizer HP, Yu HD: PBAD-based shuttle vectors for functional analysis of toxic and highly regulated genes in Pseudomonas and Burkholderia spp. and other bacteria. Appl Environ Microbiol 2008,74(23):7422–7742.PubMedCrossRef 17. Wood LF, Ohman DE: Use of cell wall

stress to characterize sigma 22 (AlgT/U) activation by regulated proteolysis and its regulon in Pseudomonas aeruginosa . Mol Microbiol 2009,72(1):183–201.PubMedCrossRef 18. Damron FH, Davis MR Jr, Withers TR, Ernst RK, Goldberg JB, Yu G, Yu HD: Vanadate and triclosan synergistically induce alginate Buspirone HCl production by Pseudomonas aeruginosa strain PAO1. Mol Microbiol 2011,81(2):554–570.PubMedCrossRef 19. Boucher JC, Schurr MJ, Deretic V: Dual regulation of mucoidy in Pseudomonas aeruginosa and sigma factor LY3039478 datasheet antagonism. Mol Microbiol 2000,36(2):341–351.PubMedCrossRef 20. Suh SJ, Silo-Suh L, Woods DE, Hassett DJ, West SE, Ohman DE: Effect of rpoS mutation on the stress response and expression of virulence factors in Pseudomonas aeruginosa . J Bacteriol 1999,181(13):3890–3897.PubMed 21. Schurr MJ, Martin DW, Mudd MH, Deretic V: Gene cluster controlling conversion to alginate-overproducing phenotype in Pseudomonas aeruginosa : functional analysis in a heterologous host and role in the instability of mucoidy. J Bacteriol 1994,176(11):3375–3382.PubMed 22.

Once again, under supervision of ED doctors, students are able to perform these procedures. Group 1 students averaged 33.9 single stitch sutures, while Group 2 students averaged 96.2 of the same procedure (a difference of 183.7% of procedures, p = 0.000032). Regarding Donatti stitches, Group 1 students reported having done an average of 5.2 sutures, while in Group 2 the recorded average

was 12.2, with a difference of 7 procedures (131% more for Group 2). (Table 1) Students have an established role in the Emergency Department, but sometimes their help is needed for trauma patients in the resuscitation room. The student on duty estimated the number of supervised visits to the trauma resuscitation room. Group 1 showed a mean of 2.8 visits,

compared with a mean of 21 visits in Group 2 (an increase of 650.2% for Epacadostat in vivo the Group 2, p = 0.000045). (Table 1) In order to achieve the clerkship objectives, it is important for the students to participate in all parts of patient care, from the patient admission in the ED to the management (discharge, admission to hospital floor, admission to ICU, admission to mini-unit, etc). However, these objectives are not required. Consequently, the study found that while students from Group 1 aided in discharging the patient, 69.1 times on average, Group 2 performed the same task 256.7 times ( a 271.5% increase for Group 2). In addition, correlation with the numbers of histories taken revealed that in Group 1, 49.6% of patients whose history had been taken were not followed up and discharged by the same student. In comparison Liothyronine Sodium to Group 2, this percentage MI-503 supplier decreases to 29.4% (p = 0.011 for Group 1, p = 0.117 for Group 2). Concerning the number of supervised prescriptions, Group 1 students wrote 56.7 prescriptions at discharge, and Group 2 students wrote 232.4 (309.9%

more). (Figure 2) Figure 2 Number histories takings in initial patient care vs number of patients discharged. Rose: Group 1 patient discharged. Light-Blue: Group 1 histories taken. Red: Group 2 patient discharged. Dark-Blue: Group 2 histories taken. Finally, students were asked about their intention to pursue a surgical career. The vast majority of students (70.6%) said they want to be surgeons, 21.6% said they have no interest in surgical careers and the remainder (7.8%) did not answer the question. Also, when asked if the participation in this clerkship influenced their choice, we found that in 41.6% of cases, the clerkship had a positive influence, 7.8% had a VRT752271 solubility dmso negative influence and 35.3% reported it did not influence their decision. However, 15.7% declined to answer the question. (Figure 3) (Figure 4) Figure 3 Percentage of Students that want to follow a surgical career. Yellow: No. Red: Not Answered. Green: Yes. Figure 4 The supervised extra-curricular practical activity influence in their Decision. Green: Yes, Positive. Yellow: Yes, Negative. Red: No.

Photosynth Res. doi:10.​1007/​s11120-010-9607-z Tachibanal M, Allen AE, Kikutani S, Endo Y, Bowler C, Matsuda Y (2011) Localization of putative carbonic anhydrases in two marine diatoms, Phaeodactylum tricornutum

and Thalassiosira pseudonana. Photosynth Res. doi:10.​1007/​s11120-011-9634-4 Tanaka T, Fukuda Y, Yoshino T, Maeda Y, Muto M, Matsumoto M, Mayama M, Matsunaga T (2011) High-throughput pyrosequencing of the Selonsertib chloroplast genome of a highly neutral-lipid-producing marine pennate diatom, Fistulifera sp. strain JPCC DA0580. Photosynth Res. doi:10.​1007/​s11120-011-9622-8 Wang Y, Duanmu D, Spalding MH (2011) Carbon dioxide concentrating mechanism in Chlamydomonas reinhardtii: inorganic carbon transport and CO2 recapture. Photosynth Res. doi:10.​1007/​s11120-011-9643-3 Yamano T, Fujita A, Fukuzawa H (2011) Photosynthetic characteristics of a multicellular green alga Volvox carteri in response to external CO2 levels possibly regulated by CCM1/CIA5 ortholog. Photosynth Res. doi:10.​1007/​s11120-010-9614-0″
“Introduction Plants need light to be able to perform photosynthesis. At the level of individual cells, the light intensity varies in an unpredictable manner. Leaves can adjust to changes in light intensity in various ways. However,

LCZ696 mw when plants are exposed to irradiances that are much higher than those they are adapted to, they use mechanisms to dissipate the excess energy (Prásil et al. 1992; Van Rensen and Curwiel 2000; Tyystjärvi 2008; Takahashi and Badger 2011). If these mechanisms are overloaded, the photosynthetic apparatus becomes damaged, leading to photoinhibition. This phenomenon

was first studied by Kok (1956). At present several hypotheses are available with respect to the primary mechanism of the photoinhibitory damage. According to the so called acceptor-side mechanism (Vass et al. 1992) reduction of the plastoquinone pool promotes double reduction, next protonation, and loss of the primary quinone electron acceptor of photosystem II (PSII), QA. In this situation, recombination reactions between QA − and P680 + can lead to the formation of triplet chlorophyll, that may react with oxygen to produce harmful https://www.selleckchem.com/products/ly3023414.html singlet oxygen. In the donor-side mechanism (Callahan et al. 1986; Anderson et al. 1998) the oxidized primary donor of PSII, P680 +, has such a high oxidative potential that it can oxidize pigment molecules if electron transfer from the oxygen evolving complex does not function, this is what sometimes appears to occur. According to the low-light mechanism (Keren et al. 1997) generation of triplet chlorophyll in recombination reactions cause photoinhibition when the electron transport is slow. In the singlet oxygen mechanism (Jung and Kim 1990), photoinhibition is initiated by generation of singlet oxygen by iron-sulfur centers or cytochromes.

The variable (inducible) part of fluorescence is expressed as F v = F m – F 0, and when normalized to F m (F v/F m) presents GDC-0941 purchase a measure of the maximum quantum yield of charge separation at PSII. Under ambient light conditions, the operational quantum yield of PSII (F v′/F m′) is obtained instead. Both parameters are useful as they respond to nutrient limitation, excess light or transiently when growth conditions change. A combination of dark- and light adapted measurements can be used to determine the electron transport rate under known irradiance(s), which can in turn be used to model primary production

(Kolber and Falkowski 1993). The current work focuses on the experimental manipulation and spectral LY3023414 clinical trial measurement of dark-adapted F v/F

m. The use of this parameter in higher level applications is discussed at length in recent reviews of literature on the subject (Suggett et al. 2004, Huot and Babin 2010). Advances in light-emitting diode (LED) manufacturing have led to the availability of Selleck CHIR-99021 narrow-band, high-power excitation light sources of high efficiency and stability. Their rapid flash capability and high output makes them the light source of choice for FRRF protocols and for PAM applications that require a small footprint. In FRRF, microsecond flashlets provide a saturating flash train within a single turnover period of PSII (<100–150 μs). PAM-type fluorometers have been developed with a combination of light sources of different colours for some time. Palmatine FRRF instruments were until very recently limited to the use of LEDs of one colour in order to produce sufficiently bright flashlets. Blue light sources have been chosen to provide overlap with the absorption by Chla and accessory photosynthetic pigments in algae, but do not overlap with cyanobacterial phycobilipigment absorption (Johnsen and Sakshaug 2007). Recent studies have shown that blue-light equipped

FRRF instruments are relatively insensitive to the presence of cyanobacteria, if these do not possess short-wavelength forms of phycoerythrin (Raateoja et al. 2004; Suggett et al. 2004). While F v/F m can be recorded from cyanobacteria using blue excitation as long as the light source can saturate PSII, the intensity of the fluorescence is relatively low compared to algae. Variable fluorescence of cyanobacteria can alternatively be assessed from orange or red excitation sources that excite the phycobilipigments in cyanobacteria (Schubert et al. 1989). Now that LEDs are available at the brightness required by FRRF instruments, this concept stands to be adapted to the FRRF range of instrumentation. Studies on the optimization of the variable fluorescence measurement towards unbiased representation of the phytoplankton community, are therefore overdue.