These initial neuroimaging studies of PIT have focused on the inf

These initial neuroimaging studies of PIT have focused on the influence of appetitively conditioned stimuli on instrumental responses maintained by positive reinforcement, and highlight the involvement of the striatum. In the current Trametinib purchase study, we sought to understand the neural correlates of PIT in an aversive Pavlovian learning situation when instrumental responding was maintained through negative reinforcement. Participants exhibited specific PIT, wherein selective

increases in instrumental responding to conditioned stimuli occurred when the stimulus signaled a specific aversive outcome whose omission negatively reinforced the instrumental response. Additionally, a general PIT effect was observed such that when a stimulus was associated with a different aversive outcome than was used to negatively reinforce instrumental behavior, the presence of that stimulus caused a non-selective increase in overall instrumental responding. Both specific and general PIT behavioral effects correlated with increased activation in corticostriatal circuitry, particularly in the striatum, a region involved in cognitive and motivational processes. These results suggest that avoidance-based PIT utilizes a similar Pirfenidone manufacturer neural mechanism to that seen with PIT in an appetitive context, which has implications

for understanding mechanisms of drug-seeking behavior during addiction and relapse. “
“This study examined changes in dendritic morphology and spine density in multiple brain regions [Zilles' areas: (i) the Cg3 region of the anterior cingulate cortex or the medial prefrontal cortex, layer III (Cg3); (ii) the dorsal agranular insular cortex, layer III (AID); (iii) the PAR I region of the parietal cortex, layer III (Par1) and (iv) the nucleus accumbens (NAc)]of Long–Evans Baf-A1 mouse rats following exposure to nicotine prenatally, in late adolescence, or both prenatally and in adolescence. Prenatal nicotine exposure induced enduring changes in neuroanatomical organisation that varied

between male and female offspring, with males exhibiting increased dendritic complexity of neurons in AID and NAc whereas females experienced increased dendritic complexity in Par1 but decreased dendritic complexity of neurons in NAc. Similarly, nicotine given in late adolescence dramatically reorganised neural circuitry of both male and female offspring, with males exhibiting decreased dendritic complexity of neurons in Par1 and Cg3 but increased dendritic complexity in AID, and females exhibiting decreased dendritic complexity in Cg3 and NAc but increased complexity in AID. Exposure to nicotine both prenatally and in adolescence produced few neuroanatomical parameters that demonstrated a prenatal experience × adolescent drug administration interaction. Females showed additive effects in Par1, Cg3 and NAc whereas males demonstrated additive effects only in AID.

Furthermore, production of mitochondrial superoxide radicals incr

Furthermore, production of mitochondrial superoxide radicals increased significantly when cells were irradiated with 411 nm light at 4.5 W/m2. In addition, such irradiation caused an activation of the antioxidative glutathion system. PI3K inhibitor Using vital staining, flow cytometry and western blotting, we were able to show that

apoptosis only took place when cells were exposed to 411 nm blue light at higher irradiances; necrosis was not observed. Enhanced caspase-3 cleavage product levels confirmed that this effect was dependent on light irradiance. Significant alterations of the above-mentioned parameters were not observed when cells were irradiated with 471 nm light despite a high irradiance of 4.5 W/m2, indicating that the cytotoxic effect of blue light is highly dependent on wavelength.

The observed phenomena in R28 cells at 411 nm (4.5 W/m2) point to an apoptosis pathway elicited by direct mitochondrial damage and increased oxidative stress. Thus, light of 411 nm should act via impairment of mitochondrial function by compromising the metabolic situation of these retinal neuronal cells. “
“There is a strong interest in harnessing the genetic manipulations that are possible in mice to investigate the functional neural mechanisms modulating the associative processes that control drug-seeking behavior. However, it is unknown whether intracranial techniques, such as the disconnection procedure commonly used in rats to examine serial connectivity between implicated areas, can be successfully applied Opaganib solubility dmso to mice. We have previously demonstrated that the expression of ethanol-seeking behavior in mice is dependent upon amygdala Etomidate (Amy) dopamine and nucleus accumbens (Acb) N-methyl-d-aspartate (NMDA) receptor activation (Gremel & Cunningham, 2009). Here, we used a neuropharmacological disconnection procedure to investigate whether dopamine activation of the Amy directly leading to increases in Acb glutamate release and binding of NMDA receptors modulates the expression

of ethanol-seeking behavior. Immediately before testing the expression of an ethanol-induced conditioned place preference, mice were given an Amy infusion of flupenthixol and either an ipsilateral or contralateral Acb infusion of AP-5. Although both ipsilateral and contralateral manipulations reduced the expression of ethanol conditioned place preference, in a separate experiment we demonstrated that a unilateral Acb infusion of AP-5, but not Amy flupenthixol, is sufficient to disrupt preference. The finding of a significant blockade by unilateral AP-5 into the Acb precludes any conclusions about a unique role for the Amy/Acb neuroanatomical connection in this model of ethanol-seeking behavior.

The largest class of natural substances, the terpenoids, also mak

The largest class of natural substances, the terpenoids, also makes up the largest number of volatile compounds detected by GC/MS as produced by Phoma sp.,

an endophyte on creosote bush (Table 1). In the case of Phoma sp. it appears that the terpenoids produced are limited to those in the category of sesquiterpenoids, although other chemical classes are also represented (Table 1). Other VOCs, as expected, are produced when the organism is grown under microaerophilic conditions (Table 2). It would appear that this is only one case out of many that may exist in nature in which a microbial learn more endophyte may mimic the biochemistry of its host in order to survive the conditions of a stressful environment. Although both the host and the endophyte do produce at least one hydrocarbon

in common, namely trans-caryophyllene, the most abundant fungal product is cis-caryophyllene or humulene (Table 1). Although the products of both the host and the endophyte are antifungal, it remains to be seen AUY-922 research buy what the role of each of these sets of products might be in the defense of the host in its native state and what role they play in the ability of the host and its endophyte/pathogen to survive a relatively harsh environment. The myriad of VOCs, such as alcohols, and other reduced products of this organism Fenbendazole have potential as bio-fuels. The endophytic/pathogenic nature of

Phoma sp. may not be unique to this organism. Other endophytic species, Pestalotiopsis spp., are well-known plant pathogens of tropical plants yet can be readily found as endophytes. The age, nutritional status and general environment of the plant more or less dictate the outcome of the host/microorganism relationship, as experimentally demonstrated by Madar et al. (1991). S.K.S. is grateful to the Department of Biotechnology (DBT), the Government of India, New Delhi, for the award of an DBT Overseas Associateship in the Niche Area of Biotechnology (No. BT/IN/BTOA/NICHE/2006 dated13 February 2008) to study at MSU, USA, and to the Department of Science and Technology (DST), New Delhi, for providing financial support to set up the National Facility for Culture Collection of Fungi (No. SP/SO/PS-55/2005) at MACS’ Agharkar Research Institute, Pune, India, and to the Director, MACS’ ARI, for granting permission to work at MSU. G.A.S. is grateful to the NSF and DoE for providing research funds. The BOYSCAST program of India granted a 1-year fellowship to S.Y.U.H. to study and work at MSU. We are grateful to Mr Darwin Whitaker who generously supplied plant materials from the Utah desert region on various occasions. “
“Spores of Bacillus subtilis are dormant cell types that are formed when the bacterium encounters starvation conditions.

In the current investigation, we monitored yeast viability using<

In the current investigation, we monitored yeast viability using

primuline following two methods of yeast rehydration: quick and slow rehydration. The first approach rehydrated cells for 10 min and this is known to fix the yeast plasma membrane in a state similar to that following dehydration– rehydration stress. Previous experiments (Beker & Rapoport, 1987) showed that it was not possible to improve the viability of such cells by prolonging their incubation in water. The second approach facilitated slow rehydration of cells in water vapour for 1 h and this led to full reparation of reversible damage to Ku-0059436 price the yeast plasma membrane, as shown previously (Rapoport et al., 2009), by detecting changes in the phase transition temperatures of yeast membrane lipids. Figure 2 shows that magnesium bioavailability did not influence the stability of yeast cells in the exponential phase of growth. It is noteworthy that very low viabilities of S. cerevisiae taken for dehydration–rehydration from the exponential growth phase are normal for this growth phase (see Beker & Rapoport, 1987). In contrast, cells taken from the stationary phase before dehydration–rehydration procedures were of higher viabilities (Fig. 2). Stationary-phase cells also exhibited maximum

resistance to dehydration–rehydration when PI3K inhibitor grown in media with 0.15 g L−1 magnesium. It is apparent that at different yeast culture growth phases, magnesium exhibited different effects on cells. Thus, exponential growth-phase supplementations with certain levels of magnesium ions promoted a higher biomass yield. In the stationary growth phase, magnesium conferred on cells a higher resistance to dehydration–rehydration treatments. It is likely that yeast cells require strictly

defined levels of Mg2+ ions for maximizing growth and stress resistance. The growth-stimulatory effects of magnesium during the exponential phase may be linked to the activation of key metabolic enzymes, such as transphosphorylases (Walker, 1999). Additionally, magnesium may exert a protective influence on dehydrated stationary growth-phase cells by acting as a charge stabilizer of cell membranes. Thus, compromising magnesium bioavailability can lead to unfavourable CYTH4 changes in yeast cell physiology, notably their ability to withstand dehydration–rehydration. The influence of calcium on yeast cell resistance to dehydration–rehydration treatments was studied using unsupplemented molasses nutrient medium (which contained optimum concentrations of Mg2+– 0.15 g L−1 of Mg2+), and the results are shown in Fig. 2. It is evident that addition of Ca2+ ions had little effect on the stability of yeast cells from the exponential growth phase with regard to dehydration–rehydration treatments. It can also be seen that the addition to the medium of 2 g L−1 of Ca2+ was accompanied by a small increase (8–10%) in the viability of dehydrated cultures from the stationary growth phase.

In the current investigation, we monitored yeast viability using<

In the current investigation, we monitored yeast viability using

primuline following two methods of yeast rehydration: quick and slow rehydration. The first approach rehydrated cells for 10 min and this is known to fix the yeast plasma membrane in a state similar to that following dehydration– rehydration stress. Previous experiments (Beker & Rapoport, 1987) showed that it was not possible to improve the viability of such cells by prolonging their incubation in water. The second approach facilitated slow rehydration of cells in water vapour for 1 h and this led to full reparation of reversible damage to Selleckchem Decitabine the yeast plasma membrane, as shown previously (Rapoport et al., 2009), by detecting changes in the phase transition temperatures of yeast membrane lipids. Figure 2 shows that magnesium bioavailability did not influence the stability of yeast cells in the exponential phase of growth. It is noteworthy that very low viabilities of S. cerevisiae taken for dehydration–rehydration from the exponential growth phase are normal for this growth phase (see Beker & Rapoport, 1987). In contrast, cells taken from the stationary phase before dehydration–rehydration procedures were of higher viabilities (Fig. 2). Stationary-phase cells also exhibited maximum

resistance to dehydration–rehydration when selleck chemical grown in media with 0.15 g L−1 magnesium. It is apparent that at different yeast culture growth phases, magnesium exhibited different effects on cells. Thus, exponential growth-phase supplementations with certain levels of magnesium ions promoted a higher biomass yield. In the stationary growth phase, magnesium conferred on cells a higher resistance to dehydration–rehydration treatments. It is likely that yeast cells require strictly

defined levels of Mg2+ ions for maximizing growth and stress resistance. The growth-stimulatory effects of magnesium during the exponential phase may be linked to the activation of key metabolic enzymes, such as transphosphorylases (Walker, 1999). Additionally, magnesium may exert a protective influence on dehydrated stationary growth-phase cells by acting as a charge stabilizer of cell membranes. Thus, compromising magnesium bioavailability can lead to unfavourable only changes in yeast cell physiology, notably their ability to withstand dehydration–rehydration. The influence of calcium on yeast cell resistance to dehydration–rehydration treatments was studied using unsupplemented molasses nutrient medium (which contained optimum concentrations of Mg2+– 0.15 g L−1 of Mg2+), and the results are shown in Fig. 2. It is evident that addition of Ca2+ ions had little effect on the stability of yeast cells from the exponential growth phase with regard to dehydration–rehydration treatments. It can also be seen that the addition to the medium of 2 g L−1 of Ca2+ was accompanied by a small increase (8–10%) in the viability of dehydrated cultures from the stationary growth phase.

Cell-free supernatants were then removed and resolved with 150 μL

Cell-free supernatants were then removed and resolved with 150 μL DMSO. The OD570 nm was measured on a microplate reader. The minimal inhibitory concentration (MIC) of farrerol and other commonly used antibiotics for each isolate was determined using the broth microdilution method with an inoculum of 5 × 105 CFU mL−1 according to the Clinical and Laboratory Standards Institute guidelines, and incubated for 24 h at 37 °C (CLSI, 2005). All tests were performed in duplicate. Bacteria were cultured in MHB at 37 °C, with graded subinhibitory concentrations of farrerol, until the postexponential

growth phase (OD600 nm of 2.5) was reached. Culture supernatants were collected by centrifugation. Total haemolysis Mitomycin C of culture supernatants were evaluated as described previously (Qiu et al., 2010b) using rabbit erythrocytes. Staphylococcus selleckchem aureus strains ATCC 29213, MRSA 2985 and MRSA 3701 were grown, and supernatants were prepared in the same manner as for

the haemolysis assay. Samples (20 μL) of culture supernatants were boiled in Laemmli sample buffer and loaded on a 12% sodium dodecyl sulphate-polyacrylamide gel (Laemmli, 1970). Western blotting was performed as described by Xiang et al. (2010) and the product instructions for Amersham ECL Western blotting detection reagents (GE Healthcare, UK). Antibody to the α-toxin was obtained from Sigma-Aldrich. A 100-μL volume of supernatant from the postexponential phase (OD600 nm of 2.5) cultures was added to 1 mL of azocasein (Sigma-Aldrich) and incubated at 37 °C for 1 h. After incubation, the reaction was stopped by adding 1 mL of 5% (w/v) trichloroacetic acid, and undigested azocasein was allowed to precipitate for 30 min. The mixture was then centrifuged at 10 000 g for 10 min, and A328 nm of the supernatant was read. Staphylococcus aureus strain ATCC 29213 was incubated with or without the addition of subinhibitory concentrations

of farrerol in the same manner as for the haemolysis assay. Total RNA from the bacterial cultures was extracted as described previously (Qiu et al., 2010a). RNA was reverse transcribed into cDNA using the TaKaRa RNA PCR kit MRIP (AMV) Ver. 3.0 (Takara, Kyoto, Japan), according to the manufacturer’s instructions. The primer pairs used in real-time RT-PCR are listed in Table 1. The PCR was performed using Sybr green. The reagents consisted of 12.5 μL 2 × SYBR Premix Ex Taq (Takara), 0.5 μL of each primer (10 μM) and 1 μL of sample cDNA in a final volume of 25 μL. The reactions were performed using the 7000 Sequence Detection System (Applied Biosystems, Courtaboeuf, France). Cycling conditions consisted of an initial denaturation step at 95 °C for 30 s, 35 cycles of 95 °C for 5 s, 55 °C for 30 s and 72 °C for 20 s. The melting curves for the PCR products were obtained by the stepwise increase of the temperature from 50 to 94 °C.

At this time, the Writing Group does not recommend the use of CD4

At this time, the Writing Group does not recommend the use of CD4 T-cell percentage to monitor disease progression in adult patients with HIV-1 infection. There are exceptions to this rule: individuals with splenectomy and patients with Human T-lymphotropic virus Type 1 (HTLV-1) coinfection [9, 10] may have a CD4 lymphocytosis and, in this instance, CD4 T-cell counts may give a misleading impression as to the true extent of

immune deficiency. Patients with these conditions should be monitored using CD4 T-cell percentage and ART should be offered to individuals with values of 21% or lower. A significant discrepancy between CD4 T-cell count and percentage should alert clinicians to potentially reversible causes of immune deficiency such as steroid and/or cytotoxic therapies, and intercurrent sepsis. Primary HIV infection is associated with a high plasma viral load. This declines about 4–6 months after infection selleck to a nearly steady level, with a small but appreciable increase observed over time during the asymptomatic phase of the infection [1, 2]. The viral load increases sharply again

in advanced disease, coinciding with the onset of AIDS. It has been long established that the set-point viral load is a strong predictor of the rate of disease progression [3-5]. While viral load results are generally highly reproducible, at least two values are required for patients with chronic Anti-infection Compound Library price infection to establish a firm set point [6]. Subsequent measurements can be taken every 6 months in asymptomatic stable

patients not receiving ART. A further measurement should be taken prior to initiation of therapy if a recent value is not available. While the CD4 T-cell count is the main driver for initiation of ART, the viral load provides additional guiding information, especially in patients with a relatively high CD4 T-cell count. In addition, the viral load may influence Galeterone the choice of antiretroviral agents [7]. The goal of ART is restoration of CD4 T-cell count and suppression of viral load below the quantification limit of commercial viral load assays, until recently 50 copies/mL. Newly introduced viral load assays, typically based on real-time polymerase chain reaction (PCR) technology, have a lower limit of quantification of 40 copies/mL (e.g. Abbott RealTime, Abbott Molecular, Abbott Park, Illinois, USA) or 20 copies/mL (e.g. Roche TaqMan v.2, Roche, Basel, Switzerland) and can report qualitative RNA detection below these thresholds. The interpretation of RNA detection below 50 copies/mL remains difficult in the absence of published evidence. While lack of RNA detection during ART may be regarded as a desirable outcome, evidence indicates that HIV-1 RNA persists at a low level in the plasma of treated patients who maintain suppression <50 copies/mL for several years [8].

p-Toluenesulfonate (TSA)

(Fig 1a) is a xenobiotic arylsu

p-Toluenesulfonate (TSA)

(Fig. 1a) is a xenobiotic arylsulfonate that is widely used in industry and that is found in seepage from landfills (Riediker et al., 2000). Biodegradation of TSA has been explored as a sole source of carbon and energy for bacteria for over 60 years (e.g. Czekalowski & Skarzynski, 1948), and three different pathways have been discovered (Focht & Williams, 1970; Locher et al., 1989; Junker et al., 1994), the best characterized of which is the tsa system in Comamonas testosteroni T-2 (Fig. 1b) (Cook et al., 1999; Providenti et al., 2001; Tralau et al., 2001, 2003a, b; Mampel et al., 2004; Monferrer et al., 2010). The overall objective of this http://www.selleckchem.com/products/Romidepsin-FK228.html project was not only to elucidate the enzymatic reactions involved in TSA degradation but also to evaluate their evolutionary origin and potential ecological significance in natural environments. Earlier work showed the world-wide occurrence of TSA degradation, including the tsa operon, but, with one exception, all isolates were from contaminated sites, for

example sewage works: the exception is ‘strain TA12’ from Moorea, an island neighboring Tahiti, French Polynesia (Tralau et al., 2001) – none of the other samples from pristine sites elsewhere in Moorea, in the coastal and marine environments (with varying human impact) of Roscoff (Brittany, France), Carna and Mace Head Co. (Galway, Ireland), Aspropyrgos (Greece) or in the selleck chemical pristine peat bog of Murnauer Moos (Bavaria, Germany) yielded any isolates growing on TSA (Tralau et al., 2001). Preliminary analyses of the genomes of C. testosteroni KF1 and Delftia acidovorans SPH1, together with Integrated Microbial Genomes software (http://img.jgi.doe.gov/cgi-bin/pub/main.cgi), indicate the widespread nature of regulons R2 (Wang et al., acetylcholine 1995, J. Ruff & A.M. Cook, unpublished data) and R4 (Providenti et al., 2001) of the tsa system in Fig. 1b (D. Schleheck & A.M. Cook, unpublished data). Furthermore, an analogue of TSA, p-toluenecarboxylate (TCA), can be considered to occur naturally in turpentine (Cahours, 1850), and the initial reaction steps in the degradation of

TCA involve the same enzymes required for TSA (Junker et al., 1996). At the onset of this study, considerable uncertainty prevailed as to the identity of isolate ‘TA12.’ In order to clarify its taxonomic affiliation and the TSA-degrading pathway of this culture unambiguously, we conducted a combination of reisolations, growth and biochemical experiments as well as sequencing of 16S rRNA genes. Strain TA12’ was obtained in earlier work, and the same complex or carbon-limited salt media were used here (Tralau et al., 2001). Isolated organisms were grown at least as six biological replicates at 28 °C in 150-μL cultures in 300-μL wells of 96-well plates in a plate reader (Synergy HT, Biotek), and all measurements were performed as 10-fold technical replicates.

morsitans, G fuscipes, G pallidipes, and G brevipalpis) was pe

morsitans, G. fuscipes, G. pallidipes, and G. brevipalpis) was performed using the Holmes–Bonner protocol (Holmes & Bonner, 1973). Nucleic acid extraction for C. columbae was performed using the QIAamp tissue mini kit (Qiagen, Valencia, CA). All samples were resuspended in 1 × Tris-EDTA following DNA isolation. DNA samples were subjected to PCR amplification of genes encoding putative outer membrane components; specifically ompA, the outer membrane protein A, ompC, the osmoporin protein C, and rcsF, ycfM, slyB, and spr, producing various outer membrane lipoproteins. PCR annealing temperatures, primers, and respective amplicon sizes are included in Supporting Information, Table S1. Notably, amplification reactions

of ycfM from C. columbae and Selleck GDC0068 C. melbae PF 01367338 and rcsF and slyB from C. columbae were not successful. Negative controls were included in each set of amplification reactions. The amplification products were analyzed by agarose gel electrophoresis and visualized with Kodak 1d image analysis software. The amplicons were purified using QIAquick PCR purification kit (Qiagen) and subject to DNA sequencing at the West Virginia University’s Department of Biology Genomics Center on an ABI 3130xl analyzer (Applied Biosystems, Foster City, CA) using a 3.1 BigDye protocol (Applied Biosystems). For each

sample, three to five amplicons were sequenced in both directions and contigs were assembled using Ridom Trace Edit (Ridom GmbH, Wurzburg Germany). The Sodalis ompA gene was amplified from two G. morsitans, G. fuscipes, G. brevipalpis, and G. pallidipes individuals. Amplicons were ligated into pGEM-T vector (Promega) and Escherichia coli JM109 cells were transformed. Four colonies per individual tsetse were verified for an ompA insertion Ixazomib clinical trial and sequenced as described above. All analyses included sequence data collected in this study or publicly available at NCBI GenBank. DNA sequences were aligned using the clustal x algorithm with default settings, and refined manually when necessary. Maximum parsimony (MP) and neighbor joining (NJ) analyses were performed with 1000 replicates in paup 4.0 (Swofford, 2002). MP heuristic searches utilized the tree-bisection-reconnection

(TBR) branch-swapping algorithm with 200 Max trees and starting trees were created using stepwise additions. All MP analyses were performed twice, where gaps were treated either as ‘missing data’ or as a ‘fifth character state,’ with no differences noted between the results. NJ analyses implemented Kimura’s two-parameter model (Kimura, 1980). Lineage support was measured by calculating nonparametric bootstrap values (n=1000) (Felsenstein, 1985). The evolutionary models used for Bayesian analyses were determined using the Akaike Information Criterion in mrmodeltest 2.3 (Nylander, 2004). Bayesian analyses were performed in mrbayes 3.1.2 (Ronquist & Huelsenbeck, 2003), and the number of categories used to approximate the gamma distribution was set at four.

Lipopolysaccharide plays important roles in symbiosis, either as

Lipopolysaccharide plays important roles in symbiosis, either as structural components or as signaling

molecules (Fraysse et al., 2003). Lipopolysaccharide, a major constituent of the outer membrane of rhizobia, consists of an outer membrane anchor A lipid connected through a core oligosaccharide to a surface-exposed O-chain polysaccharide. Proper O-polysaccharide and core structures appear to be important for symbiosis, and for structural modification during differentiation to bacteroid (Fraysse et al., 2003). In R. leguminosarum bv. viciae, the O-antigen lipopolysaccharide is essential for cell–cell interaction, and the formation of a compact, structured

biofilm (D.M. Russo, unpublished Ruxolitinib concentration data). Rhizobial adhesion proteins (known as Rap proteins) have been isolated from R. leguminosarum bv. trifolii (Ausmees et al., 2001). RapA1 is an extracellular calcium-binding protein that promotes rhizobial autoaggregation through cell poles, and is involved in attachment and rhizosphere colonization (Mongiardini et al., 2008). A RapA1-overproducing strain, in comparison with the wild-type R200 strain, showed higher adsorption to roots of the legume host red clover, and to nonsymbiotic plants such as common bean, alfalfa, and Selleckchem Sorafenib soybean (Mongiardini et al., 2008). RapA1 protein Methane monooxygenase promoted rhizobial adsorption to root surfaces. However, overproduction of the protein had no effect on attachment to inert surfaces (polystyrene wells, polypropylene beads, sand, and vermiculite), and did not increase nodulation (Mongiardini et al., 2008). These results suggest that RapA1 receptors are located only on the plant surface, and that the function of the protein may be related to early attachment and colonization of roots, but not to nodulation. Glucomannan, a polysaccharide located on one of the poles of R. leguminosarum cells, is involved in attachment to the root surface through binding to host plant lectin (Laus et

al., 2006). Glucomannan-mediated attachment to pea roots is important for competitive nodule infection (Williams et al., 2008). Similar to the findings reported by Russo et al. (2006) for strain A34, the sequenced strain 3841 forms three-dimensional biofilms on glass, with microcolonies surrounded by water channels and clusters of closely packed hexagonal cells (honeycomb-like structures) (Williams et al., 2008). Elimination of the acidic exopolysaccharide by disruption of the pssA gene led to the formation of a flat, unstructured biofilm (Williams et al., 2008), suggesting (like the findings of Russo et al., 2006) that this exopolysaccharide plays an important role in biofilm formation.