Tânia Caetano

Congeneric Lantibiotics from Ribosomal In Vivo Peptide Synthesis with Noncanonical Amino Acids

Expanded repetoire: Synthetic amino acids translated into propeptides dramatically increase the chemical diversity of the two-component lantibiotic lichenicidin. This opens new routes towards novel and unique peptide antibiotic sequences, which could display features important for medical applications.

Class I and Class II Lanthipeptides Produced by Bacillus spp.

The increasing number of multidrug-resistant pathogens, along with the small number of new antimicrobials under development, leads to an increased need for novel alternatives. Class I and class II lanthipeptides (also known as lantibiotics) have been considered promising alternatives to classical antibiotics. In addition to their relevant medical applications, they are used as probiotics, prophylactics, preservatives, and additives in cosmetics and personal-care products. The genus Bacillus is a prolific source of bioactive compounds including ribosomally and nonribosomally synthesized antibacterial peptides. Accordingly, there is significant interest in the biotechnological potential of members of the genus Bacillus as producers of antimicrobial lanthipeptides. The present review focuses on aspects of the biosynthesis, gene cluster organization, structure, antibacterial spectrum, and bioengineering approaches of lanthipeptides produced by Bacillus strains. Their efficacy and potency against some clinically relevant strains, including MRSA and VRE, are also discussed. Although no lanthipeptides are currently in clinical use, the information herein highlights the potential of these compounds.

Biomonitoring a human population inhabiting nearby a deactivated uranium mine.

Environmental exposure to uranium and its daughter radionuclides, has been linked to several negative effects such as those related with important physiological processes, like hematopoiesis, and may also be associated with genotoxicity effects. Herein, genotoxic effects, immunotoxicity, trace elements and C reactive protein (CRP) analyses, were performed in peripheral blood samples collected from individuals of a population living near a deactivated uranium mine. C reactive protein analysis was performed to exclude candidates with active inflammatory processes from further evaluations. DNA damage and immunotoxicity (immunophenotyping and immune cell counts) were evaluated by comet assay and flow cytometry, respectively. Significant DNA damage was observed in the peripheral blood samples from volunteers living in the Cunha Baixa village. A significant decrease of NK and T lymphocytes counts were observed in the individuals from the Cunha Baixa village, when compared with individuals from the reference site. Uranium and manganese levels were significantly higher in the Cunha Baixa village inhabitants. On the other hand, zinc levels were significantly lower in those individuals when compared with the volunteers from the control village. Results suggest that inhabitants from Cunha Baixa have a higher risk of suffering from serious diseases such as cancer, since high DNA damages were observed in peripheral blood leukocytes and also decreased levels of NK and T cells, which play an essential role in the defense against tumor growth.

Lichenicidin Biosynthesis in Escherichia coli: licFGEHI Immunity Genes Are Not Essential for Lantibiotic Production or Self-Protection

ABSTRACT This study demonstrated, for the first time, that immunity genes licFGEHI are not essential for self-protection and production of the two-component lantibiotic lichenicidin in the Gram-negative heterologous host Escherichia coli BLic5. Additionally, it was experimentally demonstrated that lichenicidin lantibiotics are active against the E. coli imp4213 strain, a mutant strain possessing a permeable outer membrane.

Assessment of antibiotic resistance of Escherichia coli isolates and screening of Salmonella spp. in wild ungulates from Portugal.

Antibiotic resistance is an emerging global problem. Wild animals are rarely exposed to antibiotics and therefore low levels of antibiotic resistance are expected. However, the growing interactions of these animals with humans and livestock may have a huge impact on their bacterial flora. This study aimed to assess the levels of antibiotic resistance in Escherichia coli isolated from widespread wild ungulates in Portugal. The interpretation of inhibition zone diameters was performed according to clinical breakpoints and epidemiological cut-offs, determined with the normalized resistance interpretation (NRI) method. For clinical breakpoints, 16% of the isolates were resistant to at least one antibiotic, including ampicillin (10%), tetracycline (9%), streptomycin (5%) co-trimoxazole (4%), amoxicillin/clavulanic acid (1%) and cefoxitin (1%). The levels of resistance detected in E. coli strains isolated from wild boar were statistically different for ampicillin and co-trimoxasol. According to NRI cut-offs, 10% of the population showed a non-wild-type phenotype against at least one antibiotic, also including tetracycline (9%), co-trimoxazole (6%), streptomycin (4%), ampicillin (2%) and amoxicillin/clavulanic acid (1%). Considering this parameter of comparison, no statistically different levels of resistance were identified between E. coli recovered from the three wild ungulates. Screening of Salmonella spp., which can be potentially pathogenic, was also performed, revealing that its prevalence was very low (1.5%). The study demonstrated that wild ungulates from Portugal are also reservoirs of antibiotic-resistant bacteria.

First description of blaIMP-8 in a Pseudomonas mendocina isolated at the Hospital Infante D. Pedro, Aveiro, Portugal.

Pseudomonas mendocina carrying a novel class 1 integron containing an IMP-8 gene was isolated from an inanimate surface in a female ward sanitary facility of the Hospital Infante D. Pedro, Aveiro, Portugal. Hybridization with the integrase gene (intI1) and 16S rDNA revealed that the integron is chromosomally located. Here we report for the first time the presence of an IMP-8 metallo-beta-lactamase gene in the Pseudomonas genus.

FALCON: a method to infer metagenomic composition of ancient DNA

The general approaches to detect and quantify metagenomic sample composition are based on the alignment of the reads, according to an existing database containing reference microbial sequences. However, without proper parameterization, these methods are not suitable for ancient DNA. Quantifying somewhat dissimilar sequences by alignment methods is problematic, due to the need of fine-tuned thresholds, considering relaxed edit distances and the consequent increase of computational cost. Additionally, the choice of the thresholds poses the problem of how to quantify similarity without producing overestimated measures. We propose FALCON-meta, a compression-based method to infer metagenomic composition of next-generation sequencing samples. This unsupervised alignment-free method runs efficiently on FASTQ samples. FALCON-meta quickly learns how to give importance to the models that cooperate to predict similarity, incorporating parallelism and flexibility for multiple hardware characteristics. It shows substantial identification capabilities in ancient DNA without overestimation. In one of the examples, we found and authenticated an ancient Pseudomonas bacteria in a Mammoth mitogenome. FALCON-meta can be accessed at https://github.com/pratas/falcon.

Pedobacter lusitanus sp. nov., a new bacterial species isolated from sludge of a deactivated uranium mine in Portugal.

Strain NL19T is a Gram-stain-negative, aerobic bacterium that was isolated from sludge of a deactivated uranium mine in Portugal. 16S rRNA gene sequence analysis revealed that strain NL19T is a member of the genus Pedobacter and closely related to the strains Pedobacter himalayensis MTCC 6384T, Pedobacter cryoconitis DSM 14825T, Pedobacter westerhofensis DSM 19036T and Pedobacterhartonius DSM 19033T. It had a DNA G+C content of 40.8 mol%, which agreed with the genus description. The main fatty acids included C16 : 1ω7c, C14 : 1ω5c, C4 : 0, iso-C17 : 0, iso-C17 : 0 3-OH, C16 : 0, anteiso-C15 : 0 and iso-C15 : 0 3-OH. The main lipids present were phospholipids (60 %) and sphingolipids (35 %). The most abundant phospholipids included phosphatidylethanolamine, phosphatidylinositol and phosphatidylcholine. Menaquinone-7 (MK-7) was the only isoprenoid quinone detected. DNA-DNA hybridization similarities between strain NL19T and Pedobacter himalayensis MTCC 6384T, Pedobacter cryoconitis DSM 14825T, Pedobacter westerhofensis DSM 19036T and Pedobacter hartonius DSM 19033T were 15.3 , 16.2 , 11.5 and 16.0 %, respectively. Strain NL19T can also be distinguished from these four species based on gyrB and intergenic transcribed spacers (ITS) sequences and by some phenotypic traits such as NaCl tolerance, pH, growth temperature and carbon source utilization. Strain NL19Trepresents a novel species of the genus Pedobacter, for which the name Pedobacter lusitanus sp. nov. is proposed. The type strain is NL19T (=LMG 29220T=CECT 9028T). An amended description of Pedobacter himalayensis is also included.

A novel complex class 1 integron found in a Klebsiella pneumoniae isolate from Portugal.

Klebsiella pneumoniae Kp1 carrying a novel complex class 1 integron was isolated from an inanimate surface of a female ward sanitary facility in the Hospital Infante D. Pedro, Aveiro, central Portugal. The integron consists of two variable regions (VRs); VR1 was previously described in Escherichia coli and Vibrio cholerae, and VR2 contains an In37-like structure and is located downstream of an ISCR1 element. The integron was found on a plasmid of 225 kb. The qnrB10 gene, although present, is not associated with the complex class 1 integron.

The lanthipeptides of Bacillus methylotrophicus and their association with genomic islands.

Bacillus methylotrophicus strains are known for their potential as plant-growth promoters and as microbial pesticides that effectively control plant diseases caused by bacteria and fungi. Over the past few years, a wide diversity of their secondary metabolites has been extensively characterized. Among these are the RiPPs lanthipeptides, which are an important and growing group of notable compounds. The increasing interest in B. methylotrophicus species, accompanied by the development of high throughput sequencing techniques, has resulted in a substantial number of full genomes being available. Here, an in silico analysis was performed on these genomes in order to survey the presence of lanthipeptide biosynthetic clusters. It was found that the pan genome of B. methylotrophicus only encoded the biosynthesis of mersacidin and amylolysin, which are lanthipeptides with antibacterial activity. However, the amylolysin gene cluster identified was comprised of more genetic elements than those previously described, and it had certain features of two-peptide lantibiotics. Additionally, it was also established that the association of lanthipeptides with genomic islands (GIs) was not confined to mersacidin. This was also found for the amylolysin cluster as well as other class I and class II lanthipeptides, supporting the idea that their production is probably related to functional adaptation.