Optimization of antimicrobial peptides for the application against biocorrosive bacteria.

Microbiologically influenced corrosion is a common problem in the industrial field due to the deterioration of metals in the presence of various microorganisms, in particular sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB). A common method to reduce microbiologically influenced corrosion is the application of biocides. The limited number of suitable biocides and the resulting development of resistance, high dosage, and high application rate hinder an effective application. An environmentally friendly alternative could be the application of antimicrobial peptides (AMP), which have already been established in the field of medical devices for a while. Here, the successful treatment of different AMPs against 3 SRB and 1 SOB was demonstrated. The peptide L5K5W was favored due to its broad activity, high stability, and simple structure resulting in low synthesis costs. An alanine scan showed that substitution of leucine with tryptophan increased the activity of this peptide twofold compared to the original peptide against D. vulgaris, the main representative of SRB. Additional optimization of this modified peptide through changes in amino acid composition and lipidations significantly increased the effectiveness, finally resulting in a minimum inhibitory concentration (MIC) of 15.63 µg/mL against Desulfovibrio vulgaris. Even against the marine SRB Desulfovibrio indonesiensis with a required salt concentration of min. 2%, an activity of the peptides can be observed (MIC: 31.25 µg/mL). The peptides also remained stable and active for 7 days in the supernatant of the bacterial culture. KEY POINTS: • Antimicrobial peptides provide an alternative to combat biocorrosive bacteria. • Optimization of the peptide sequence leads to a significant increase in activity. • The investigated peptides exhibit high stability, both in the medium and in the bacterial supernatant.

First Report of Blackleg Disease Caused by Leptosphaeria maculans on Canola in Brazil.

Canola (Brassica napus L.) is a relatively new crop in Brazil, having been grown there for approximately 8 years. In 2000, leaf lesions and stem cankers were observed in cvs. Hyola 420 and Hyola 401 in farmers' fields in the state of Rio Grande do Sul. Cankered stems were received at the University of Manitoba, Canada, from Rio Grande do Sul for disease identification. Small pieces of the stem were cut from the cankered area, and standard protocol was followed to surface sterilize the stem pieces. Stem pieces were plated on V8 agar medium and incubated under light for 12 days. Typical fungal colonies with concentric rings containing pycnidia formed on the V8 agar. The colony characteristics were typical of the blackleg pathogen, Leptosphaeria maculans (Desmaz.) Ces. & De Not. (anamorph = Phoma lingam) (Tode:Fr.) Desmaz.). Blackleg is an economically important and serious disease in many parts of the world including Australia, Canada, the United States, and Europe. L. maculans strains can be characterized in four pathogenicity groups (PG1 through PG4) based on differential testing procedures giving interaction phenotype (IP) reactions (2). Two weeks after plating on V8 media, plates were flooded with sterile distilled water, and pycnidiospores were harvested. Flats of multipots filled with Metro Mix were seeded with three cultivars (Westar, Glacier, and Quinta). One-week-old cotyledons from the three cultivars were inoculated with pycnidiospore suspensions (2 × 107 pycnidiospores per ml) of seven Brazilian isolates, numbered 7, 8, 9, 11, 15, 16, and 18, respectively. Each cotyledon leaf, punctured in the center with a needle, was inoculated with a 10-µl droplet of the inoculum. Disease evaluations were made 11 days after inoculation using a 0 to 9 rating scale (1). This screening was repeated three times from February 2001 to October 2001. After the second repeat, the isolates from Rio Grande do Sul were passed through the highly susceptible canola cv. Westar. Results from all four trials were consistent, and yielded one PG1 isolate (No. 7) and six PG3 isolates. PG1 is classified as a nonaggressive strain, whereas PG3 isolates are classified as aggressive. PG3 isolates would have an IP reaction of 7 to 9, 7 to 9, and 3 to 6 on cvs. Westar, Glacier, and Quinta, respectively. PG2 is the most commonly found aggressive strain in the Canadian prairies. PG3 is predominantly found in Australia, the United Kingdom, and the United States. To our knowledge, this is the first report of blackleg disease caused by L. maculans on canola in Brazil. Differential testing fulfilled Koch's postulates and determined the PG groups found in Brazil (PG1 and PG3). References: (1) P. A. Delwiche. Genetic aspects of blackleg (Leptosphaeria maculans) resistance in rapeseed (Brassica napus) Ph.D. thesis. University of Wisconsin-Madison, 1980. (2) A. Mengistu et al. Plant Dis. 75:1279, 1991.

Firearm-related injuries in Canada: issues for prevention.

We reviewed the available data on firearm-related injuries in Canada to suggest strategies for prevention in the context of the proposed amendments to the Criminal Code (Bill C-17) currently before Parliament. The risk of death from a firearm in Canada is equivalent to the risk of death from a motor vehicle crash. We discuss the risks associated with firearms with regard to suicides, homicides and "accidents." We also discuss the accessibility of firearms. This article builds upon a recently published update on the epidemiologic basis of the public health approach for the prevention of firearm-related injuries and deaths. The key to the etiologic approach to preventing such injuries and deaths is to view the incidents, regardless of their medicolegal circumstances, as having one factor in common: the discharge of a firearm.