Closely related fungi employ diverse enzymatic strategies to degrade plant biomass.

BACKGROUND: Plant biomass is the major substrate for the production of biofuels and biochemicals, as well as food, textiles and other products. It is also the major carbon source for many fungi and enzymes of these fungi are essential for the depolymerization of plant polysaccharides in industrial processes. This is a highly complex process that involves a large number of extracellular enzymes as well as non-hydrolytic proteins, whose production in fungi is controlled by a set of transcriptional regulators. Aspergillus species form one of the best studied fungal genera in this field, and several species are used for the production of commercial enzyme cocktails. RESULTS: It is often assumed that related fungi use similar enzymatic approaches to degrade plant polysaccharides. In this study we have compared the genomic content and the enzymes produced by eight Aspergilli for the degradation of plant biomass. All tested Aspergilli have a similar genomic potential to degrade plant biomass, with the exception of A. clavatus that has a strongly reduced pectinolytic ability. Despite this similar genomic potential their approaches to degrade plant biomass differ markedly in the overall activities as well as the specific enzymes they employ. While many of the genes have orthologs in (nearly) all tested species, only very few of the corresponding enzymes are produced by all species during growth on wheat bran or sugar beet pulp. In addition, significant differences were observed between the enzyme sets produced on these feedstocks, largely correlating with their polysaccharide composition. CONCLUSIONS: These data demonstrate that Aspergillus species and possibly also other related fungi employ significantly different approaches to degrade plant biomass. This makes sense from an ecological perspective where mixed populations of fungi together degrade plant biomass. The results of this study indicate that combining the approaches from different species could result in improved enzyme mixtures for industrial applications, in particular saccharification of plant biomass for biofuel production. Such an approach may result in a much better improvement of saccharification efficiency than adding specific enzymes to the mixture of a single fungus, which is currently the most common approach used in biotechnology.

Discovery and development of a synthetic peptide derived from lactoferrin for clinical use.

There is an urgent need to develop new antimicrobial drugs especially for combating the rise of infections caused by multi-resistant pathogens such as MRSA and VRSA. The problem of antibiotic resistant micro-organisms is expected to increase disproportionally and controlling of infections is becoming difficult because of the rapid spread of those micro-organisms. Primary therapy with classical antibiotics is becoming more ineffective. Combinational therapy of antibiotics with antimicrobial peptides (AMP's) has been suggested as an alternative approach to improve treatment outcome. Their unique mechanism of action and safety profile makes AMP's appealing candidates for simultaneous or sequential use in different cases of infections. In this review, for antimicrobial treatment the application of synthetic antimicrobial peptide hLF(1-11), derived from the first 11 amino acids of human lactoferrin is evaluated in both pre-clinical and clinical settings. Present information indicates that this derivate from lactoferrin is well tolerated in pre-clinical tests and clinical trials and thus hLF(1-11) is an interesting candidate for further exploration in various clinical indications of obscure infections, including meningitis. Another approach of using AMP's is their use in prevention of infections e.g. as coating for dental or bone implants or in biosensing applications or useful as infection specific radiopharmaceutical.

Various routes of administration of (99m)Tc-labeled synthetic lactoferrin antimicrobial peptide hLF 1-11 enables monitoring and effective killing of multidrug-resistant Staphylococcus aureus infections in mice.

The synthetic antimicrobial peptide representative of the first 11 N-terminal amino acids of human lactoferrin (hLF 1-11) kills multidrug-resistant Staphylococcus aureus (MRSA). This study displays antimicrobial activity of hLF 1-11, via various routes of administration, against MRSA infections in mice. Radiolabeling hLF 1-11 with technetium-99m ((99m)Tc-hLF 1-11) enables scintigraphic monitoring directly after administration. (99m)Tc-hLF 1-11 was taken up by the gall bladder, intestines, and kidneys. Most of the radioactivity was captured in the urinary bladder and about 1% of the injected dose accumulated into infected thigh muscles. At 2 or 24h after either intravenously, subcutaneously, intraperitoneally, or orally injected a single dose of 0.04 mg/kg hLF 1-11 in mice significantly reduced (20-60 times) the number of viable MRSA. In a dose-response setting in immunocompetent mice maximum bactericidal effects (10,000 times reduction) of intravenously injected (99m)Tc-hLF 1-11 was seen with 40 mg/kg whereas the same dose of orally administered (99m)Tc-hLF 1-11 induced about approximately 100 times reduction. In conclusion, intravenously and orally administrated (99m)Tc-hLF 1-11 accumulates in infected tissues and is highly effective against experimental infections with MRSA. Moreover, scintigraphy is an excellent tool to study the pharmacology of experimental compounds and to determine the uptake in infected tissues.

The pharmacology of radiolabeled cationic antimicrobial peptides.

Cationic antimicrobial peptides are good candidates for new diagnostics and antimicrobial agents. They can rapidly kill a broad range of microbes and have additional activities that have impact on the quality and effectiveness of innate responses and inflammation. Furthermore, the challenge of bacterial resistance to conventional antibiotics and the unique mode of action of antimicrobial peptides have made such peptides promising candidates for the development of a new class of antibiotics. This review focuses on antimicrobial peptides as a topic for molecular imaging, infection detection, treatment monitoring and additionally, displaying microbicidal activities. A scintigraphic approach to studying the pharmacokinetics of antimicrobial peptides in laboratory animals has been developed. The peptides were labeled with technetium-99m and, after intravenous injection into laboratory animals, scintigraphy allowed real-time, whole body imaging and quantitative biodistribution studies of delivery of the peptides to the various body compartments. Antimicrobial peptides rapidly accumulated at sites of infection but not at sites of sterile inflammation, indicating that radiolabeled cationic antimicrobial peptides could be used for the detection of infected sites. As the number of viable micro-organisms determines the rate of accumulation of these peptides, radiolabeled antimicrobial peptides enabled to determine the efficacy of antibacterial therapy in animals to be monitored as well to quantify the delivery of antimicrobial peptides to the site of infection. The scintigraphic approach provides to be a reliable method for investigating the pharmacokinetics of small cationic antimicrobial peptides in animals and offers perspective for diagnosis of infections, monitoring antimicrobial therapy, and most important, alternative antimicrobial treatment infections with multi-drug resistant micro-organisms in humans.

Human lactoferrin-derived peptide's antifungal activities against disseminated Candida albicans infection.

BACKGROUND: Because the human lactoferrin-derived peptide, hLF(1-11), exerts potent in vitro candidacidal activity, we investigated whether it displays antifungal activity against disseminated Candida albicans infections. METHODS: Neutropenic mice were intravenously infected with C. albicans and, 24 h later, were injected with hLF(1-11); 18 h later, the number of viable yeasts in the kidneys was determined microbiologically, the size and number of infectious foci were determined histologically, and serum cytokine levels were determined by immunoassays. RESULTS: hLF(1-11) was effective (maximum reduction, 1.5 logs) against disseminated C. albicans infections, and its antifungal activity leveled off at a concentration of 0.4 ng of hLF(1-11)/kg of body weight. The antifungal activity of hLF(1-11) was increased in mice injected with interleukin (IL)-10 neutralizing antibodies, which suggests that IL-10 reduces the antifungal activity of hLF(1-11). In agreement with this result was the finding that injection of high doses of hLF(1-11) into infected mice was accompanied by increased levels of IL-10 in serum. Microscopic analysis revealed that infectious foci in kidneys of hLF(1-11)-treated mice contained mainly blastoconidia, whereas filamentous forms were abundant in untreated mice. The peptide inhibited the in vitro morphological transition of C. albicans, in a dose-dependent manner. : hLF(1-11) is effective against disseminated C. albicans infections; and its effects on C. albicans viability and virulence and on host cells may explain this antifungal activity.

Histatin-derived monomeric and dimeric synthetic peptides show strong bactericidal activity towards multidrug-resistant Staphylococcus aureus in vivo.

Homodimerization of histatin-derived peptides generally led to improved bactericidal activity against Staphylococcus aureus in vitro. In vivo, monomers and dimers were equally active in killing bacteria in mice with a soft tissue infection. Altogether, these peptides are promising compounds for the development of novel therapeutics against infections with drug-resistant bacteria.

Synthetic peptides derived from human antimicrobial peptide ubiquicidin accumulate at sites of infections and eradicate (multi-drug resistant) Staphylococcus aureus in mice.

The presence and antimicrobial activity of antimicrobial peptides (AMPs) has been widely recognized as an evolutionary preserved part of the innate immune system. Based on evidence in animal models and humans, AMPs are now positioned as novel anti-infective agents. The current study aimed to evaluate the potential antimicrobial activity of ubiquicidin and small synthetic fragments thereof towards methicillin resistant Staphylococcus aureus (MRSA), as a high priority target for novel antibiotics. In vitro killing of MRSA by synthetic peptides derived from the alpha-helix or beta-sheet domains of the human cationic peptide ubiquicidin (UBI 1-59), allowed selection of AMPs for possible treatment of MRSA infections. The strongest antibacterial activity was observed for the entire peptide UBI 1-59 and for synthetic fragments comprising amino acids 31-38. The availability, chemical synthesis opportunities, and size of these small peptides, combined with their strong antimicrobial activity towards MRSA make these compounds promising candidates for antimicrobial therapy and detection of infections in man.

Histatin and lactoferrin derived peptides: antimicrobial properties and effects on mammalian cells.

In order to analyze the clinical potential of two antimicrobial peptides, human lactoferrin 1-11 (hLF1-11) and synthetic histatin analogue Dhvar-5, we measured the killing effect on bacteria, and the potential toxicity on erythrocytes and bone cells. The antimicrobial activity was determined in a killing assay on six strains, including methicillin resistant Staphylococcus Aureus. The effect on human erythrocytes and MC3T3 mouse bone cells was measured with a hemolysis assay and a viability assay, respectively. Both hLF1-11 and Dhvar-5 dose-dependently killed all bacterial strains, starting at concentrations of 6 microg/mL. hLF1-11 had no effect on mammalian cells at concentrations up to 400 microg/mL, but Dhvar-5 induced significant hemolysis (37% at 200 microg/mL) and bone cell death (70% at 400 microg/mL). This indicates that both peptides are able to kill various resistant and non-resistant bacteria, but Dhvar-5 may exert a cytotoxic effect on host cells at higher concentrations.

The synthetic N-terminal peptide of human lactoferrin, hLF(1-11), is highly effective against experimental infection caused by multidrug-resistant Acinetobacter baumannii.

The lactoferrin-derived peptide hLF(1-11), but not its control peptide, was highly effective against five multidrug-resistant Acinetobacter baumannii strains in vitro (3 to 4 log reduction) and against four of these strains in an experimental infection in mice (2 to 3 log reduction). Therefore, this peptide is a promising candidate as a novel agent against infections with multidrug-resistant A. baumannii.

Release of calcium from intracellular stores and subsequent uptake by mitochondria are essential for the candidacidal activity of an N-terminal peptide of human lactoferrin.

OBJECTIVES: Earlier studies showed that mitochondrial damage is a hallmark of the candidacidal activity of an N-terminal peptide of human lactoferrin, further referred to as hLF(1-11). Since uptake of Ca(2+) by mitochondria may be essential for their activation, the aim of this study was to define the role of Ca(2+) in killing of Candida albicans by the hLF(1-11) peptide. METHODS: The effect of compounds interfering with Ca(2+) homeostasis on the hLF(1-11)-induced candidacidal activity, changes in mitochondrial membrane potential, and reactive oxygen species production were evaluated using a killing assay, rhodamine 123 staining, and 2',7'-dichlorofluorescein diacetate, respectively. The increase in cellular Ca(2+) content was measured using (45)Ca(2+). RESULTS: Our results revealed that Ruthenium Red, which inhibits the mitochondrial Ca(2+)-uniporter and the voltage-sensitive Ca(2+) release from internal stores, blocked (P<0.05) the hLF(1-11)-induced candidacidal activity as well as changes in the membrane potential of mitochondria, and reactive oxygen species production. Oxalate, which precipitates Ca(2+) in intracellular organelles, decreased (P<0.05) the peptide-induced changes in the membrane potential of mitochondria, reactive oxygen species production, and candidacidal activity. Furthermore, the Ca(2+) ionophore ionomycin combined with high CaCl(2) concentrations enhanced the hLF(1-11)-induced candidacidal activity. Moreover, hLF(1-11) caused an influx of Ca(2+) from the extracellular medium into C. albicans reaching a three-fold increase at 2 h, whereas no increase was found in unexposed cells. In agreement, the Ca(2+)-chelator EGTA blocked the peptide-induced candidacidal activity. CONCLUSIONS: Ca(2+) release from intracellular stores, probably through subsequent mitochondrial Ca(2+) uptake, is essential for the hLF(1-11)-induced candidacidal activity.

99mTc-Labeled UBI 29-41 peptide for monitoring the efficacy of antibacterial agents in mice infected with Staphylococcus aureus.

UNLABELLED: Based on our earlier observation that (99m)Tc-UBI 29-41, a radiolabeled peptide derived from ubiquicidin (UBI), discriminates between infections and sterile inflammatory processes, we considered the possibility that this tracer could be used for monitoring the efficacy of antibacterial agents in animals infected with Staphylococcus aureus. METHODS: We injected (99m)Tc-UBI 29-41 into S. aureus-infected mice after treatment with various doses of cloxacillin or erythromycin. At intervals thereafter, accumulation of the radiolabeled peptide at the site of infection was assessed by scintigraphy. When S. aureus was antibiotic resistant, we evaluated the efficacy of hLF 1-11, an antimicrobial peptide derived from human lactoferrin (hLF), in rats using (99m)Tc-UBI 29-41 and scintigraphy. RESULTS: Decreasing amounts of radiolabeled peptide at the site of the S. aureus infection in animals correlated (r(2) > 0.81; P < 0.001) with increasing doses of cloxacillin in animals. An effective dose of erythromycin resulted in reduced (P = 0.023) accumulation of the radiolabeled peptide at the site of S. aureus infection in mice. In addition, we noted decreasing amounts of (99m)Tc-UBI 29-41 at the site of infection after administration of increasing doses of hLF 1-11 peptide in rats infected with antibiotic-resistant S. aureus. Furthermore, the number of viable bacteria decreased with increasing doses of cloxacillin or hLF 1-11 peptide, and a good correlation (r(2) > 0.80; P < 0.001) between the accumulation of (99m)Tc-UBI 29-41 and the number of viable (antibiotic-resistant) S. aureus at the site of infection was seen. In an attempt to explain these results, we found that these antibacterial agents do not affect the in vitro binding of (99m)Tc-UBI 29-41 to bacteria. Furthermore, this radiolabeled peptide bound to free bacteria and to cell-adherent but not phagocytized S. aureus, suggesting that at sites of infection mainly extracellular bacteria are targeted by (99m)Tc-UBI 29-41. CONCLUSION: (99m)Tc-UBI 29-41 allows the monitoring of the efficacy of antibacterial agents in mice and rats with S. aureus infections.

Synergistic activity of the N-terminal peptide of human lactoferrin and fluconazole against Candida species.

In light of the need for new antifungal regimens, we report that at noncandidacidal concentrations, the lactoferrin-derived peptide hLF(1-11), which is highly active against fluconazole-resistant Candida albicans, acts synergistically with fluconazole against this yeast and a fluconazole-sensitive C. albicans strain as well as C. glabrata, C. krusei, C. parapsilosis, and C. tropicalis. When these yeasts were exposed to hLF(1-11) for 5 min and then incubated with fluconazole, they were killed effectively, while no candidacidal activity was observed when they were incubated first with fluconazole and then exposed to the peptide, indicating that the candidacidal activity is initiated by the peptide while fluconazole is only required during the effector phase. Investigations of the effect of azide, which inhibits mitochondrial respiration, on the activity of combinations of hLF(1-11) and fluconazole against fluconazole-resistant C. albicans revealed that it inhibits this activity, even when added during the effector phase only. As expected, azide inhibited the accumulation of rhodamine 123 in mitochondria and the production and release of ATP by C. albicans that occurred upon exposure to the combination of hLF(1-11) and fluconazole. Accordingly, oxidized ATP (oATP), an antagonist of ATP receptors, completely blocked the candidacidal activity of the hLF(1-11)-fluconazole combination, whereas oATP did not block the activity when its presence was restricted to the effector phase. The candidacidal activity of combinations of hLF(1-11) and fluconazole, which is initiated by the peptide through the involvement of energized mitochondria, renders fluconazole-resistant C. albicans sensitive to this azole.