Quantification of the CBD-FITC conjugates surface coating on cellulose fibres

Multi-layer encapsulation of pumpkin (Cucurbita maxima L.) seed protein hydrolysate and investigating its release and antioxidant activity in simulated gastrointestinal digestion

Because of their high protein content, easy access and low cost, pumpkin seeds are a valuable raw material for the preparation of antioxidant protein hydrolysates. Micro-coating is an effective method to protect bioactive compounds against destruction. In order to strengthen the alginate hydrogel network loaded with pumpkin seed protein hydrolysate (PSPH), CMC was added as part of its formulation in the first step, and chitosan coating was used in the second step. Then, swelling amount, release in the simulated gastrointestinal environment (SGI), antioxidant activity after SGI, Fourier transform infrared spectroscopy (FTIR), zeta potential, dynamic light scattering (DLS), polydispersity index (PDI) and scanning electron microscopy (SEM) of the samples were evaluated. The results showed that, the swelling amount of the chitosan-alginate hydrogel was lower than the chitosan-alginate-CMC sample, and with the increase in chitosan concentration, the swelling amount decreased. The release amount in the chitosan-alginate sample was higher than that in the chitosan-alginate-CMC sample, and with the increase in chitosan concentration, the release rate decreased. Also, the amount of release increased with the passage of time. The highest antioxidant activity belonged to the chitosan-alginate sample in SGI, and it increased with increasing the chitosan concentration. All findings demonstrated that the use of multi-component hybrid systems is a useful method for the protection of bioactive compounds against destruction, their antioxidant activities and their release behavior.

Strategies on biosynthesis and production of bioactive compounds in medicinal plants

Medicinal plants are a valuable source of essential medicines and herbal products for healthcare and disease therapy. Compared with chemical synthesis and extraction, the biosynthesis of natural products is a very promising alternative for the successful conservation of medicinal plants, and its rapid development will greatly facilitate the conservation and sustainable utilization of medicinal plants. Here, we summarize the advances in strategies and methods concerning the biosynthesis and production of natural products of medicinal plants. The strategies and methods mainly include genetic engineering, plant cell culture engineering, metabolic engineering, and synthetic biology based on multiple "OMICS" technologies, with paradigms for the biosynthesis of terpenoids and alkaloids. We also highlight the biosynthetic approaches and discuss progress in the production of some valuable natural products, exemplifying compounds such as vindoline (alkaloid), artemisinin and paclitaxel (terpenoids), to illustrate the power of biotechnology in medicinal plants.

An Efficient and Easy- to- Use Method for Extraction of H. pylori DNA from Archival Formalin-Fixed and Paraffin-Embedded Gastric Tissues

Background & Objective

Formalin-fixed paraffin-embedded archived tissues are useful for the genetic analyses and assessment of some patients' disease history, including infectious diseases. However, there is no established protocol for extracting bacterial DNA from the archived specimens. In this study DNA was extracted from the archived H. pylori-positive gastric biopsies by some modifications applied to the previously published protocols. The quality of the extracted DNA was assessed by amplifying H. pylori-specific 16S rRNA gene.

Methods

Fifty H. pylori-positive gastric biopsies obtained, fixed, and embedded in paraffin blocks during 2002-2008 were recruited. After paraffin removal, simultaneous proteinase K treatment and mechanical disruption using glass beads were used for the digestion of gastric tissues. DNA extraction was performed by adding one step of phenol treatment and two steps of incubation to the conventional phenol-chloroform method. The quantity and quality of the extracted DNA samples were assessed. Also, PCR was performed using primers specific for the H. pylori-specific 16S rRNA.

Results

The electrophoresis showed that intact DNAs were recovered from all biopsy samples. Amplification of the PCR products with the size of 519bp confirmed the presence of H. pylori-specific 16S rRNA gene in all the biopsies.

Conclusion

A 100% success rate for the amplification of H. pylori-specific 16S rRNA gene was achieved from all the samples. In this regard, the designed modified method resulted in the effective removal of interfering contaminations and enhanced the quality of the extracted bacterial DNA from the archived tissues. These modifications may contribute to better extraction of the intact DNA from different bacteria present in human tissues.

Molecular insight into how the position of an abasic site and its sequence environment influence DNA duplex stability and dynamics

Local perturbations to DNA base-pairing stability from lesions and chemical modifications can alter the stability and dynamics of an entire oligonucleotide. End effects may cause the position of a disruption within a short duplex to influence duplex stability and structural dynamics, yet this aspect of nucleic acid modifications is often overlooked. We investigate how the position of an abasic site (AP site) impacts the stability and dynamics of short DNA duplexes. Using a combination of steady-state and time-resolved spectroscopy and molecular dynamics simulations, we unravel an interplay between AP-site position and nucleobase sequence that controls energetic and dynamic disruption to the duplex. The duplex is disrupted into two segments by an entropic barrier for base pairing on each side of the AP site. The barrier induces fraying of the short segment when an AP site is near the termini. Shifting the AP site inward promotes a transition from short-segment fraying to fully encompassing the barrier into the thermodynamics of hybridization, leading to further destabilization the duplex. Nucleobase sequence determines the length scale for this transition by tuning the barrier height and base-pair stability of the short segment, and certain sequences enable out-of-register base pairing to minimize the barrier height.

A novel phage display vector for selection of target-specific peptides

Intrinsic low display level of polypeptides on phage is a fundamental and limiting hurdle in successful isolation of target-specific binders by phage display technology. To circumvent this challenge, we optimized the copy number of peptides displayed on the phage surface using type 33 phage vector. We randomized the first 67 amino acids of the wild type PIII to identify mutants that would result in its reduced expression. Consequently, the display level was improved by 30-fold due to higher incorporation of the synthetic PIII-peptide fusion protein on the phage surface. Utilization of this novel phage vector should provide a solid basis for the discovery of therapeutic peptides.

Construction of a novel Escherichia coli expression system: relocation of lpxA from chromosome to a constitutive expression vector

The selective marker in the plasmid-based expression system is usually a gene that encodes an antibiotic-resistant protein; therefore, the antibiotic has to add to maintain the plasmid when growing the bacteria. This antibiotic addition would lead to increase of production cost and the environment contamination. In this study, a novel Escherichia coli expression system, the lpxA deletion mutant harboring an lpxA-carrying vector, was developed. To develop this system, three plasmids pCas9Cre, pTF-A-UD, and pRSFCmlpxA were constructed. The plasmid pCas9Cre produces enzymes Cas9, λ-Red, and Cre and can be cured by growing at 42 °C; pTF-A-UD contains several DNA fragments required for deleting the chromosomal lpxA and can be cured by adding isopropyl-D-thiogalactopyranoside; pRSFCmlpxA contains the lpxA mutant lpxA123 and CamR. When E. coli were transformed with these three plasmids, the chromosomal lpxA and the CamR in pRSFCmlpxA can be efficiently removed, resulting in an E. coli lpxA mutant harboring pRSFlpxA. The lpxA is essential for the growth of E. coli; its relocation from chromosome to a constitutive expression vector is an ideal strategy to maintain the vector without antibiotic addition. The lpxA123 in pRSFlpxA can complement the deletion of the chromosomal lpxA and provide a strong selective pressure to maintain the plasmid pRSFlpxA. This study provides an experimental evidence that this novel expression system is convenient and efficient to use and can be used to improve L-threonine biosynthesis in the wild type E. coli MG1655 and an L-threonine producing E. coli TWF006.

The Use of MicroRNA Decoy Technologies to Inhibit miRNA Function in Arabidopsis

The study of gene function is best achieved through the generation of loss-of-function mutants. However, for many plant microRNAs (miRNAs), this has proven challenging, as they often belong to sequence-related families, which are encoded by multiple genes that are functionally redundant. To overcome this issue, transgenic methods have been developed that express miRNA decoys, which can sequester and inhibit families of sequence-related miRNAs. This includes miRNA MIMICs, SHORT TANDEM TARGET MIMICs, and miRNA SPONGEs. Here, we describe the methods to generate transgenic Arabidopsis that express these miRNA decoys in order to determine miRNA function.

Isolation, characterization and efficacy of phage MJ2 against biofilm forming multi-drug resistant Enterobacter cloacae

Biofilm is involved in a variety of infections, playing a critical role in the chronicity of infections. Enterobacter cloacae is a biofilm-forming and multi-drug-resistant (MDR) nosocomial pathogen leading to significant morbidity and mortality. This study aimed at isolation of a bacteriophage against MDR clinical strain of E. cloacae and its efficacy against bacterial planktonic cells and biofilm. A bacteriophage MJ2 was successfully isolated from wastewater and was characterized. The phage exhibited a wide range of thermal and pH stability and demonstrated considerable adsorption to host bacteria in the presence of CaCl₂ or MgCl₂. Transmission electron microscopy (TEM) showed MJ2 head as approximately 62 and 54 nm width and length, respectively. It had a short non-contractile tail and was characterized as a member of the family Podoviridae [order Caudovirales]. The phage MJ2 was found to possess 11 structural proteins (12-150 kDa) and a double-stranded DNA genome with an approximate size of 40 kb. The log-phase growth of E. cloacae both in biofilm and suspension was significantly reduced by the phage. The E. cloacae biofilm was formed under different conditions to evaluate the efficacy of MJ2 phage. Variable reduction pattern of E. cloacae biofilm was observed while treating it for 4 h with MJ2, i.e., biofilm under static conditions. The renewed media with intervals of 24, 72, and 120 h showed biomass decline of 2.8-, 3-, and 3.5-log, respectively. Whereas, the bacterial biofilm formed with dynamic conditions with refreshing media after 24, 72, and 120 h demonstrated decline in growth at 2.5-, 2.6-, and 3.3-log, respectively. It was, therefore, concluded that phage MJ2 possessed considerable inhibitory effects on MDR E. cloacae both in planktonic and biofilm forms.

Functional Role of Tyr12 in the Catalytic Activity of Novel Zeta-like Glutathione S-transferase from Acidovorax sp. KKS102

Glutathione S-transferases (GSTs) are a family of enzymes that function in the detoxification of variety of electrophilic substrates. In the present work, we report a novel zeta-like GST (designated as KKSG9) from the biphenyl/polychlorobiphenyl degrading organism Acidovorax sp. KKS102. KKSG9 possessed low sequence similarity but similar biochemical properties to zeta class GSTs. Functional analysis showed that the enzyme exhibits wider substrate specificity compared to most zeta class GSTs by reacting with 1-chloro-2,4-dinitrobenzene (CDNB), p-nitrobenzyl chloride (NBC), ethacrynic acid (EA), hydrogen peroxide, and cumene hydroperoxide. The enzyme also displayed dehalogenation function against dichloroacetate, permethrin, and dieldrin. The functional role of Tyr12 was also investigated by site-directed mutagenesis. The mutant (Y12C) displayed low catalytic activity and dehalogenation function against all the substrates when compared with the wild type. Kinetic analysis using NBC and GSH as substrates showed that the mutant (Y12C) displayed a higher affinity for NBC when compared with the wild type, however, no significant change in GSH affinity was observed. These findings suggest that the presence of tyrosine residue in the motif might represent an evolutionary trend toward improving the catalytic activity of the enzyme. The enzyme as well could be useful in the bioremediation of various types of organochlorine pollutants.

A Small Cellulose-Binding-Domain Protein (CBD1) in Phytophthora is Highly Variable in the Non-binding Amino Terminus

The small cellulose-binding-domain protein CBD1 is tightly bound to the cellulosic cell wall of the plant pathogenic stramenopile Phytophthora infestans. Transgene expression of the protein in potato plants also demonstrated binding to plant cell walls. A study was undertaken using 47 isolates of P. infestans from a worldwide collection, along with 17 other Phytophthora species and a related pathogen Plasmopara halstedii, to determine if the critical cell wall protein is subject to amino acid variability. Within the amino acid sequence of the secreted portion of CBD 1, encoded by the P. infestans isolates, 30 were identical with each other, and with P. mirabilis. Four isolates had one amino acid difference, each in a different location, while one isolate had two amino acid substitutions. The remaining 13 isolates had five amino acid changes that were each in identical locations (D17/G, D31/G, I32/S, T43/A, and G50/A), suggesting a single origin. Comparison of P. infestans CBD1 with other Phytophthora species identified extensive amino acid variation among the 60 amino acids at the amino terminus of the protein, and a high level of conservation from G61, where the critical cellulose-binding domain sequences begin, to the end of the protein (L110). While the region needed to bind to cellulose is conserved, the region that is available to interact with other cell wall components is subject to considerable variation, a feature that is evident even in the related genus Plasmopara. Specific changes can be used in determining intra- and inter-species relatedness. Application of this information allowed for the design of species-specific primers for PCR detection of P. infestans and P. sojae, by combining primers from the highly conserved and variable regions of the CBD1 gene.

Effect of Formulation and Process Parameters on Chitosan Microparticles Prepared by an Emulsion Crosslinking Technique

There are many studies about the synthesis of chitosan microparticles; however, most of them have very low production rate, have wide size distribution, are difficult to reproduce, and use harsh crosslinking agents. Uniform microparticles are necessary to obtain repeatable drug release behavior. The main focus of this investigation was to study the effect of the process and formulation parameters during the preparation of chitosan microparticles in order to produce particles with narrow size distribution. The technique evaluated during this study was emulsion crosslinking technique. Chitosan is a biocompatible and biodegradable material but lacks good mechanical properties; for that reason, chitosan was ionically crosslinked with sodium tripolyphosphate (TPP) at three different ratios (32, 64, and 100%). The model drug used was acetylsalicylic acid (ASA). During the preparation of the microparticles, chitosan was first mixed with ASA and then dispersed in oil containing an emulsifier. The evaporation of the solvents hardened the hydrophilic droplets forming microparticles with spherical shape. The process and formulation parameters were varied, and the microparticles were characterized by their morphology, particle size, drug loading efficiency, and drug release behavior. The higher drug loading efficiency was achieved by using 32% mass ratio of TPP to chitosan. The average microparticle size was 18.7 μm. The optimum formulation conditions to prepare uniform spherical microparticles were determined and represented by a region in a triangular phase diagram. The drug release analyses were evaluated in phosphate buffer solution at pH 7.4 and were mainly completed at 24 h.

Exploring the structure of glutamate racemase from Mycobacterium tuberculosis as a template for anti-mycobacterial drug discovery

Glutamate racemase (MurI) is responsible for providing D-glutamate for peptidoglycan biosynthesis in bacteria and has been a favoured target in pharmaceutical drug design efforts. It has recently been proven to be essential in Mycobacterium tuberculosis, the causative organism of tuberculosis, a disease for which new medications are urgently needed. In the present study, we have determined the protein crystal structures of MurI from both M. tuberculosis and Mycobacterium smegmatis in complex with D-glutamate to 2.3 Å and 1.8 Å resolution respectively. These structures are conserved, but reveal differences in their active site architecture compared with that of other MurI structures. Furthermore, compounds designed to target other glutamate racemases have been screened but do not inhibit mycobacterial MurI, suggesting that a new drug design effort will be needed to develop inhibitors. A new type of MurI dimer arrangement has been observed in both structures, and this arrangement becomes the third biological dimer geometry for MurI found to date. The mycobacterial MurI dimer is tightly associated, with a KD in the nanomolar range. The enzyme binds D- and L-glutamate specifically, but is inactive in solution unless the dimer interface is mutated. We created triple mutants of this interface in the M. smegmatis glutamate racemase (D26R/R105A/G194R or E) that have appreciable activity (kcat=0.056-0.160 min(-1) and KM=0.26-0.51 mM) and can be utilized to screen proposed antimicrobial candidates for inhibition.

Synthetic genetic polymers: advances and applications

Advances and applications of synthetic genetic polymers (xeno-nucleic acids) are reviewed in this article. The types of synthetic genetic polymers are summarized. The basic properties of them are elaborated and their technical applications are presented. Challenges and prospects of synthetic genetic polymers are discussed.

The binding of cellulase variants to dislocations: a semi-quantitative analysis based on CLSM (confocal laser scanning microscopy) images

Binding of enzymes to the substrate is the first step in enzymatic hydrolysis of lignocellulose, a key process within biorefining. During this process elongated plant cells such as fibers and tracheids have been found to break into segments at irregular cell wall regions known as dislocations or slip planes. Here we study whether cellulases bind to dislocations to a higher extent than to the surrounding cell wall. The binding of fluorescently labelled cellobiohydrolases and endoglucanases to filter paper fibers was investigated using confocal laser scanning microscopy and a ratiometric method was developed to assess and quantify the abundance of the binding of cellulases to dislocations as compared to the surrounding cell wall. Only Humicola insolens EGV was found to have stronger binding preference to dislocations than to the surrounding cell wall, while no difference in binding affinity was seen for any of the other cellulose variants included in the study (H. insolens EGV variants, Trichoderma reesei CBHI, CBHII and EGII). This result favours the hypothesis that fibers break at dislocations during the initial phase of hydrolysis mostly due to mechanical failure rather than as a result of faster degradation at these locations.

Magnetically guided chemical locomotion of self-propelling paperbots

Magneto-catalytic paperbots employing nanoparticle-coated waste papers in which the magnetic control is infused by a coating of printer ink.

Glycosylation of Cellulases: Engineering Better Enzymes for Biofuels

Cellulose in plant cell walls is the largest reservoir of renewable carbon on Earth. The saccharification of cellulose from plant biomass into soluble sugars can be achieved using fungal and bacterial cellulolytic enzymes, cellulases, and further converted into fuels and chemicals. Most fungal cellulases are both N- and O-glycosylated in their native form, yet the consequences of glycosylation on activity and structure are not fully understood. Studying protein glycosylation is challenging as glycans are extremely heterogeneous, stereochemically complex, and glycosylation is not under direct genetic control. Despite these limitations, many studies have begun to unveil the role of cellulase glycosylation, especially in the industrially relevant cellobiohydrolase from Trichoderma reesei, Cel7A. Glycosylation confers many beneficial properties to cellulases including enhanced activity, thermal and proteolytic stability, and structural stabilization. However, glycosylation must be controlled carefully as such positive effects can be dampened or reversed. Encouragingly, methods for the manipulation of glycan structures have been recently reported that employ genetic tuning of glycan-active enzymes expressed from homogeneous and heterologous fungal hosts. Taken together, these studies have enabled new strategies for the exploitation of protein glycosylation for the production of enhanced cellulases for biofuel production.

Doxorubicin-loaded magnetic gold nanoshells for a combination therapy of hyperthermia and drug delivery

In the present work, nanohybrid of an anticancer drug, doxorubicin (Dox) loaded gold-coated superparamagnetic iron oxide nanoparticles (SPIONs@Au) were prepared for a combination therapy of cancer by means of both hyperthermia and drug delivery. The Dox molecules were conjugated to SPIONs@Au nanoparticles with the help of cysteamine (Cyst) as a non-covalent space linker and the Dox loading efficiency was investigated to be as high as 0.32 mg/mg. Thus synthesized particles were characterized by HRTEM, UV-Vis, FT-IR, SQUID magnetic studies and further tested for heat and drug release at low frequency oscillatory magnetic fields. The hyperthermia studies investigated to be strongly influenced by the applied frequency and the solvents used. The Dox delivery studies indicated that the drug release efficacy is strongly improved by maintaining the acidic pH conditions and the oscillatory magnetic fields, i.e. an enhancement in the Dox release was observed from the oscillation of particles due to the applied frequency, and is not effected by heating of the solution. Finally, the in vitro cell viability and proliferation studies were conducted using two different immortalized cell lines containing a cancerous (MCF-7 breast cancer) and non-cancerous H9c2 cardiac cell type.

Bilayer mucoadhesive microparticles for the delivery of metoprolol succinate: Formulation and evaluation

Metoprolol succinate is a very potent drug for the treatment of hypertension but suffers from poor bioavailability due to its erratic absorption in lower GI tract. Therefore, in the present study, it was hypothesized that by formulating mucoadhesive particles, the residence time in the GIT and release of drug may be prolonged that will enhance the bioavailability of metoprolol succinate. Metoprolol succinate loaded chitosan microparticles were prepared by ionic gelation method. The optimized microparticles were coated with sodium alginate to form a layer over chitosan microparticles to increase the mucoadhesive strength and to release the drug in controlled manner. Coated and uncoated microparticles were evaluated for particle size, zeta potential, morphology, entrapment efficiency, drug loading and in vitro drug release. The coated microparticles showed comparatively less drug release in the 0.1 N HCl while sustained release in PBS (pH 6.8) as compared to uncoated microparticles. The in vivo study on albino rats demonstrated an increase in bioavailability of the coated microparticles as compared to marketed formulation. From the study it can be concluded that alginate coated chitosan microparticles could be a useful carrier for the oral delivery of metoprolol succinate.

Quinone-dependent alcohol dehydrogenases and FAD-dependent alcohol oxidases

This review considers quinone-dependent alcohol dehydrogenases and FAD-dependent alcohol oxidases, enzymes that are present in numerous methylotrophic eu- and prokaryotes and significantly differ in their primary and quaternary structure. The cofactors of the enzymes are bound to the protein polypeptide chain through ionic and hydrophobic interactions. Microorganisms containing these enzymes are described. Methods for purification of the enzymes, their physicochemical properties, and spatial structures are considered. The supposed mechanism of action and practical application of these enzymes as well as their producers are discussed.

The chemical basis of serine palmitoyltransferase inhibition by myriocin

Sphingolipids (SLs) are essential components of cellular membranes formed from the condensation of L-serine and a long-chain acyl thioester. This first step is catalyzed by the pyridoxal-5'-phosphate (PLP)-dependent enzyme serine palmitoyltransferase (SPT) which is a promising therapeutic target. The fungal natural product myriocin is a potent inhibitor of SPT and is widely used to block SL biosynthesis despite a lack of a detailed understanding of its molecular mechanism. By combining spectroscopy, mass spectrometry, X-ray crystallography, and kinetics, we have characterized the molecular details of SPT inhibition by myriocin. Myriocin initially forms an external aldimine with PLP at the active site, and a structure of the resulting co-complex explains its nanomolar affinity for the enzyme. This co-complex then catalytically degrades via an unexpected 'retro-aldol-like' cleavage mechanism to a C18 aldehyde which in turn acts as a suicide inhibitor of SPT by covalent modification of the essential catalytic lysine. This surprising dual mechanism of inhibition rationalizes the extraordinary potency and longevity of myriocin inhibition.

Biological pretreatment of cellulose: enhancing enzymatic hydrolysis rate using cellulose-binding domains from cellulases

In this study, cellulose-binding domains (CBDs) of cellulases from Trichoderma reesei were used in a pretreatment step and were found to effectively reduce the crystallinity of cellulose (both Avicel and fibrous cellulose). This, in turn, led to higher glucose concentrations (up to 25% increase) in subsequent hydrolysis of cellulose using a mixture of cellulases and without the need for any intermediate purification step. CBDs were shown to be active in a range of temperatures (up to 50°C), while cellulase hydrolytic activity was greatly reduced after incubation at 50°C. This was explained by retention of full binding capacity after incubation at 50°C for 15 h. Our findings suggest that CBDs may be a valuable tool in pretreating cellulose and eventually afford faster enzymatic conversion of cellulose to glucose, thus contributing to more affordable processes in the production of biofuels.

Surface display of human lactoferrin using a glycosylphosphatidylinositol-anchored protein of Saccharomyces cerevisiae in Pichia pastoris

A cell surface display system was developed in Pichia pastoris using the gene TIP1, encoding the glycosylphosphatidylinositol (GPI)-anchored protein of Saccharomyces cerevisiae (ScTIP). Human lactoferrin cDNA (hLf) was fused to a full-length TIP1 DNA (ScTIP ( 630 )) or a short-TIP1 fragment (ScTIP ( 120 )) encoding the 40 C-terminal amino acids of ScTIP. Both hLf-ScTIP fusion genes were expressed in P. pastoris SMD 1168. The fused protein was detected by western blotting after extraction of the lysed recombinant cells with Triton X-100, urea, and Triton X-100 plus urea, suggesting that the hLf is associated with the membrane. The localization of surface-displayed hLf was confirmed by immunofluorescence confocal microscopy and flow cytometric analysis using FITC-labeled anti-hLf antibody, suggesting that hLf was successfully located at the surface of P. pastoris. The intact recombinant cells and cell lysates showed antibacterial activity against target microorganisms, meaning that the expressed hLf was biologically active. The results indicated that the ScTIP anchoring motif is useful for cell surface display of foreign proteins in P. pastoris.

Phage control of dual species biofilms of Pseudomonas fluorescens and Staphylococcus lentus

Despite the recent enthusiasm for using bacteriophages as bacterial control agents, there are only limited studies concerning phage interaction with their respective hosts residing in mixed biofilm consortia and especially in biofilms where the host species is a minor constituent. In the present work, a study was made of mono and dual species biofilms formed by Pseudomonas fluorescens (Gram-negative) and/or Staphylococcus lentus (Gram-positive) and their fate after infection with phages. The dual species biofilms consisted predominantly of S. lentus. The exposure of these biofilms to a cocktail containing both P. fluorescens and S. lentus phages effectively killed and removed the hosts from the substratum. Additionally, this cocktail approach also controlled the hosts released from the biofilms to the planktonic phase. The ability of phages to control a host population present in minority in the mixed species biofilm was also assessed. For this objective, the biofilms were challenged only with phage phiIBB-PF7A, specific for P. fluorescens and the results obtained were to some extent unpredicted. First, phiIBB-PF7A readily reached the target host and caused a significant population decrease. Secondly, and surprisingly, this phage was also capable of causing partial damage to the biofilms leading to the release of the non-susceptible host (S. lentus) from the dual species biofilms to the planktonic phase. The efficiency of phage treatment of biofilms was to some extent dependent on the number of cells present and also conditioned by the infection strategy (dynamic or static) utilized in the infection of the biofilms. Nevertheless, in most circumstances phages were well capable of controlling their target hosts.