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Antimicrobial resistance continues to pose a threat to health and wellbeing. Unmitigated, it is predicted to be the leading cause of death by 2050. Hence, the sustained development of novel antibiotics is crucial. As over 60% of licensed antibiotics are based on scaffolds derived from less than 1% of all known bacterial species, bacterial secondary metabolites constitute an untapped source of novel antibiotics. The aim of this project therefore was to expand the chemical space of bacteria-derived antibiotic lead compounds, using genomics approach. To that end, a topsoil sample was collected from the rhizosphere in which antibiosis occurs naturally. Using starvation stress, sixty-five isolates were recovered from the sample, out of which four were selected based on morphology and designated A13BB, A23BA, A13AA and A23AA. A13BB was identified by 16S rRNA gene sequence comparison as a Pseudomonas spp. and the other three isolates as Hafnia/Obesumbacterium spp. A database search showed that species belonging to these genera have genomes larger than the 3 Mb size above which an increasing proportion of a bacterial genome is dedicated to secondary metabolism. Given their ecological origin, expected genome size and ability to withstand starvation stress, these four isolates were presumed to harbour antibiotic-encoding gene clusters. Isolates A13BB and A23BA were therefore selected for genome mining in the first instance. Illumina and GridION/MinION sequencing data were obtained for both isolates and assembled into high-quality genomes. Isolates' identities were confirmed by FastANI analysis as strains of P. fragi and H. alvei, with 4.94 and 4.77 Mb genomes, respectively. Assembled genomes were mined with antiSMASH. Amongst other secondary metabolite biosynthetic gene clusters (smBGCs) detected, the β-lactone smBGCs in both genomes were selected for activation as their end products bear the hallmarks of an 'ideal antibiotic' that can inhibit several bacteria-specific enzymes simultaneously. Analysis of these smBGCs revealed genes encoding two core enzymes: 2-isopropylmalate synthase (2-IPMS) and acyl CoA ligase homologues. In the biosynthetic pathway, 2-IPMS catalyses the condensation of acetyl CoA with the degradation product of valine or isoleucine to form 2-IPM. 2-IPM is isomerised to 3-IPM which then forms the β-lactone warhead through reactions catalysed by acyl CoA ligase. It was speculated that the β-lactone compound is biosynthesised to efficiently rid the organism of potentially harmful metabolic intermediates as it grows on poor carbon and nitrogen sources. Strain fermentation was therefore performed with 10.8 mM acetate as the main carbon source, and 5 mM L-valine or L-isoleucine as the nitrogen source. Fermentation extracts were analysed by LC-MS with at least thirty-seven metabolite ions detected. Many of these ions have masses in the range m/z 230-750, which is an ideal mass range for antibiotic molecules. As β-lactone compounds are difficult to identify in crude extracts, especially when utilising single-stage mass spectrometry, reactivity-guided screening of extracts with cysteine thiol probe was performed as the probe forms UV- and MS-visible adducts with β-lactone compounds. However, complete dimerization of probe at a faster-than-expected rate in extract matrices hindered successful screening. This meant that it was not possible to determine if any crude extract components were β-lactone compounds without further analysis. Measures to limit or eliminate probe dimerization are proposed, together with molecular networking strategies that can afford global visualisation and rapid dereplication of extract components, using tandem mass spectrometry fragmentation patterns of parent ions. This project provides an original and robust workflow that serves as a strong starting point in the isolation of novel β-lactone compounds from crude extracts, followed by structural optimisation and bioactivity profiling. The hitherto unrecognised potential of β-lactone natural compounds as 'ideal antibiotics' is highlighted, and several structural optimisation strategies required to harness this potential are proposed. The genomes assembled here, and associated data have been deposited in the repositories of the International Nucleotide Sequence Database Collaboration for repurposing by other researchers. Likewise, the hidden metabolic and biosynthetic potentials of P. fragi and H. alvei species uncovered by RASTtk and antiSMASH analyses have been catalogued and placed in the public domain, with many of these attributes reported for the first time.

Background: The mortality rate of cancer, one of the leading causes of death globally is continuously increasing. Despite the progress in preparing and approving conventional chemotherapeutic drugs, new forms of the diseases are evolving. Hence, an urgent need for alternative therapy .Objectives: To prepare combinatory drugs composed of nucleoside-metallophthalocyanine and a single-walled carbon complex as a potential anti-cancer agent.The complex is a major key player in photodynamic therapy. Cytidine, a nucleoside which is a major component of ribonucleic acid was chemically linked to zinc tetra-phenoxycarboxy phthalocyanine (1), a photoactive compound represented as ZnTCPC-cytidine (2). Complex 2 was adsorbed on single-walled carbon nanotube (SWCNT) represented as ZnTCPC-cytidine-SWCNT (3).Methods: Complexes 1, 2 and 3 were characterized using UV-visible and Fourier transform infrared (FTIR) spectroscopy. The photophysical properties such as fluorescence quantum and triplet quantum yield were studied using fluorescence emission and laser flash spectroscopy respectively.Results: The absorption spectra show that complex 1, 2 and 3 have the characteristics Q-band of metallophthalocyanine compounds, the FTIR spectra also confirmed that the cytidine was chemically linked to ZnTCPC, while ZnTCPC-cytidine was successfully adsorbed on SWCNT through π-π stacking. The fluorescence quantum yields were 0.10, 0.098 and 0.130, while the triplet quantum yield was 0.49, 0.76 and 0.78 for complex 1, 2 and 3 respectively.Conclusions: The triplet quantum yield result showed that complexes 2 and 3 can generate high singlet oxygen, the cytotoxic agent responsible for the irreversible destruction of cancerous cells. Hence, these complexes would find application as potential anticancer drugs for photodynamic therapy. Keywords: Zinc tetra-phenoxycarboxy phthalocyanine, Single-walled carbon nanotubes, cytidine, fluorescence and triplet quantum yields

Most variants of bacteria are resistant to traditional antibiotics which are organic. To overcome the growing infections, bacteria resistant infections, and multiple drug resistance (MDR) rates, transition metals with biological importance were coordinated to organic ligands (Ibuprofen and Salicylic acid) with anti-inflammatory properties. In this study, metal complexes of mixed Ibuprofen and Salicylic acid were prepared using a standard method to give of the type [M(Ibu)(Sal)X] (where M = Fe2+, Ni2+, Cu2+, and X = Cl2, Ibu = Ibuprofen, Sal = Salicylic acid). The complexes were characterized by UV-visible spectroscopy, conductivity measurements, melting points, FT-IR, and X-ray diffraction. The metal ions are coordinated to the ligands via the carboxylato oxygen donor atoms of both ligands. From the physicochemical data, the complexes are non-electrolytes. The XRD study suggested that the metal complexes possess a well-defined crystalline structure with average crystallite sizes of < 62 nm. Evaluations of the antimicrobial activities of the ligands and their complexes against gram-positive bacteria (S. aureus, B. subtilis, S. faecalis) and gram-negative bacteria (K. pneumonia, E. coli, and P. aeroginosa) via standard method were utilized to determine the zones of inhibition. The complexes exhibited a higher zone of inhibition, indicating higher antimicrobial activities when compared to the parent ligand. The results revealed that the metal-drug complexes are promising chemotherapeutic agents with wide spectrum of activities. Keywords: Metal-drug complexes; Ibuprofen; Spectra studies; Salicylic acid; Antimicrobial activity

Objectives The role of rhizosphere microbiome in supporting plant growth under biotic stress is well documented. Rhizobacteria ward off phytopathogens through various mechanisms including antibiosis. We sought to recover novel antibiotic-producing bacterial strains from soil samples collected from the rhizosphere. Pseudomonas fragi A13BB was recovered as part of this effort, and the whole genome was sequenced to facilitate mining for potential antibiotic-encoding biosynthetic gene clusters. Data description Here, we report the complete genome sequence of P. fragi A13BB obtained from de novo assembly of Illumina MiSeq and GridION reads. The 4.94 Mb genome consists of a single chromosome with a GC content of 59.40%. Genomic features include 4410 CDSs, 102 RNAs, 3 CRISPR arrays, 3 prophage regions, and 37 predicted genomic islands. Two β-lactone biosynthetic gene clusters were identified; besides, metabolic products of these are known to show antibiotic and/or anticancer properties. A siderophore biosynthetic gene cluster was also identified even though P. fragi is considered a non-siderophore producing pseudomonad. Other gene clusters of broad interest identified include those associated with bioremediation, biocontrol, plant growth promotion, or environmental adaptation. This dataset unveils various un−/underexplored metabolic or biosynthetic potential of P. fragi and provides insight into molecular mechanisms underpinning these attributes.

Objectives The urgent need for novel antibiotics cannot be overemphasized. Hafnia alvei A23BA was isolated from plant rhizosphere as part of an effort to recover novel antibiotic-producing bacterial strains from soil samples. The genome of the isolate was sequenced to facilitate mining for potential antibiotic-encoding biosynthetic gene clusters and to gain insights into how these gene clusters could be activated. Data description Here, we report the complete genome sequence of H. alvei A23BA obtained from the hybrid assembly of Illumina HiSeq and GridION reads. The genome, consisting of a circular chromosome and a circular plasmid, is 4.77 Mb in size with a GC content of 48.77%. The assembly is 99.5% complete with genomic features including 4,217 CDSs, 125 RNAs, and 30 pseudogenes. Thiopeptide, beta-lactone, siderophore, and homoserine lactone biosynthetic gene clusters were also identified. Other gene clusters of interest include those associated with bioremediation, biocontrol, and plant growth promotion- all of which are reported for H. alvei for the first time. This dataset serves to expedite the exploration of the biosynthetic and metabolic potentials of the species. Furthermore, being the first published genome sequence of a soil isolate, this dataset enriches the comparative genomics study of H. alvei strains.

Composition of ultra-minimal substrate medium

The urgent need for new antibiotics cannot be overemphasized. Bacterial secondary metabolites remain a relatively untapped source of new therapies. The ability to produce these bioactive compounds is however not universal to all bacterial species. Two key indicators are bacterial genome size (>3 Mb), and the presence of antibiotic-encoding biosynthetic gene cluster (BGCs) within the genomes. BGC distribution is largely determined by phylogeny. Another attribute of some antibiotic producers is the ability to withstand nutritional stress. We exploited these attributes to isolate and identify potential antibiotic producers. A minimal substrate medium was used to isolate nutritionally versatile bacterial strains from topsoil collected from the rhizosphere. The genera of isolates were identified by 16S rRNA gene sequence comparison as Pseudomonas, Hafnia and Obesumbacterium. The typical genome size of species in these genera are 6.2 Mb, 4.7 Mb and 5.0 Mb respectively. The antiSMASH database was browsed by phylogeny to determine the distribution pattern of BGCs in these genera. Pseudomonas strains have an average of 7 BGCs within their genomes that may encode antibiotics, whilst Hafnia and Obesumbacterium strains have 2 and 0 respectively. Therefore, the isolated Pseudomonas strain has the greatest potential to biosynthesis antibiotics. However, the biosynthetic potential of other isolates may be understated given the typical genome size of species in their genera, and their ecological origin. Consequently, all isolates are prime candidates for the next stage of the project which involves genome mining for cryptic or silent genes that may encode novel compounds with antibiotic properties. More isolates are also being recovered.