Isolation of chlorine-containing antibiotic from the freshwater cyanobacterium Scytonema hofmanni

Antifouling potential of cyanobacteria: a mini-review

Cyanobacteria produce a variety of bioactive metabolites that may have allelochemical functions in the natural environment, such as in the prevention of fouling by colonising organisms. Chemical compounds from cyanobacteria are also of biotechnological interest, especially for clinical applications, because of their antibiotic, algicidal, cytotoxic, immunosupressive and enzyme inhibiting activities. Cyanobacterial metabolites have the potential for use in antifouling technology, since they show antibacterial, antialgal, antifungal and antimacrofouling properties which could be expoited in the prevention of biofouling on man-made substrata in the aquatic environment. Molecules with antifouling activity represent a number of types including fatty acids, lipopeptides, amides, alkaloids, terpenoids, lactones, pyrroles and steroids. The isolation of biogenic compounds and the determination of their structure may provide leads for future development of, for example, environmentally friendly antifouling paints. An advantage of exploring the efficacy of cyanobacterial products is that the organisms can be grown in mass culture, which can be manipulated to achieve optimal production of bioactive substances. Phycotoxins and related products from cyanobacteria may serve as materials for antimicro- and antimacrofouling applications. A survey of antibiotic compounds with antifouling potential revealed more than 21 different antifouling substances from 27 strains of cyanobacteria.

Distribution and diversity of natural product genes in marine and freshwater cyanobacterial cultures and genomes

Natural products are a functionally diverse class of biochemically synthesized compounds, which include antibiotics, toxins, and siderophores. In this paper, we describe both the detection of natural product activities and the sequence identification of gene fragments from two molecular systems that have previously been implicated in natural product production, i.e., nonribosomal peptide synthetases (NRPSs) and modular polyketide synthases (PKSs), in diverse marine and freshwater cyanobacterial cultures. Using degenerate PCR and the sequencing of cloned products, we show that NRPSs and PKSs are common among the cyanobacteria tested. Our molecular data, when combined with genomic searches of finished and progressing cyanobacterial genomes, demonstrate that not all cyanobacteria contain NRPS and PKS genes and that the filamentous and heterocystous cyanobacteria are the richest sources of these genes and the most likely sources of novel natural products within the phylum. In addition to validating the use of degenerate primers for the identification of PKS and NRPS genes in cyanobacteria, this study also defines numerous gene fragments that will be useful as probes for future studies of the synthesis of natural products in cyanobacteria. Phylogenetic analyses of the cyanobacterial NRPS and PKS fragments sequenced in this study, as well as those from the cyanobacterial genome projects, demonstrate that there is remarkable diversity and likely novelty of these genes within the cyanobacteria. These results underscore the potential variety of novel products being produced by these ubiquitous organisms.

Regio and diastereoselective lactonisation of enolisable 1,3-dicarbonyls by reaction with mesoionic 1,3-oxazolium-5-olates

The one-pot reaction of enolisable 1,3-dicarbonyls and N-methyl-1,3-oxazolium-5-olate derivatives provided enol lactones directly in good yield and with excellent regio- and diastereocontrol.

Regioselective cyclization of alpha,omega-alkynoic acids catalysed by TpRu complexes: synthesis of endocyclic enol lactones [Tp = hydrotris(pyrazolyl)borate]

The sigma-enynyl complex [TpRu(C(Ph)=C(Ph)C identical to CPh)(P-MeiPr2)] efficiently catalyses the regioselective cyclization of alpha,omega-alkynoic acids to yield endocyclic enol lactones having ring size up to 12 atoms.

Kasumigamide, an antialgal peptide from the cyanobacterium Microcystis aeruginosa

Kasumigamide (1), a novel antialgal tetrapeptide containing an N-terminal alpha-hydroxy acid, was isolated from the freshwater cyanobacterium Microcystis aeruginosa (NIES-87). Its structure was elucidated by two-dimensional (1)H-(1)H and (1)H-(13)C NMR correlation experiments and confirmed by mass spectral and amino acid analyses. The absolute stereochemistry of 1 was determined by chemical studies. This peptide showed an antialgal activity against the green alga Chlamydomonas neglecta (NIES-439).

Antibiotic production by the cyanobacteria Oscillatoria angustissima and Calothrix parietina

The accumulation of antibiotic in the medium is temperature dependent and not in direct proportion to growth parameters. The cyanobacterial product suppressed growth of some natural isolates of cyanobacteria and green algae. It inhibits the growth rate and oxygen evolution of the green alga, Chlorella fusca. The antibiotic also inhibits the growth of bacteria and some fungi, especially the dermatophytes. Generally eukaryotic organisms were less sensitive than prokaryotic. Experimental mice were unaffected by the antibiotic. The Oscillatoria antibiotic does not structurally resemble to cyanobacterin.

Inhibitory metabolites production by the cyanobacterium Fischerella muscicola

Broad-spectrum inhibitory metabolites were produced by a benthic cyanobacterium Fischerella muscicola (UTEX 1829) in batch culture. These metabolites inhibited the growth of eukaryotic algae, cyanobacteria and eubacteria. The effect of culture age on the production and leakage of these inhibitory metabolites from the cyanobacterium was studied. Confirmation of the presence of an allelochemical, possibly fischerellin was achieved using high performance liquid chromatography (HPLC). The cyanobacterium produced inhibitory metabolites intracellularly at all stages of its growth cycle.

Broad spectrum and mode of action of an antibiotic produced by Scytonema sp. TISTR 8208 in a seaweed-type bioreactor

A photobioreactor was constructed using anchored polyurethane foam strips (1 x 1 x 40 cm) fixed onto a stainless-steel ring to prevent flotation, as a biomass support material (BSM). This type of reactor was named a seaweed-type bioreactor. A filamentous cyanobacterium, Scytonema sp. TISTR 8208, which produces a novel cyclic dodecapeptide antibiotic, was immobilized in seaweed-type photobioreactor and cultivated with air containing 5% CO2 sparged at a gas flow rate of 250 mL/min under illumination at a light intensity of 200 mmol photon m-2 s-1. The antibiotic produced in the seaweed-type photobioreactor was purified by HPLC and examined regarding its spectrum and mode of action. The antibiotic effectively inhibited the growth of Gram-positive bacteria, pathogenic yeasts, and filamentous fungi, but it had only a weak effect on Gram-negative bacteria. Scanning electron micrograph analysis showed that the most characteristic change was swelling of the cells after exposure to the antibiotic. The antibiotic seems to alter the conformation of the microbial cell membrane, thereby changing its permeability, leading to osmotic shock.

Algal biotechnology

The review gives a general outline of macro- and microalgal biotechnology. The main methods by which algae are cultivated and harvested are described. The first section deals with the environmental factors affecting mass culture and the principles governing the design and operation of mass cultivation systems. The second section gives the main current and potential uses of algae: in wastewater treatment, a source of food and feed, an energy source, and in the production of common and fine chemicals, such as polysaccharides, lipids, glycerol, pigments, and enzymes. Pharmaceutical uses of algae are described, and their potential as a source of novel biologically-active compounds is discussed. Future developments and the great potential of algae are considered.

Production, by filamentous, nitrogen-fixing cyanobacteria, of a bacteriocin and of other antibiotics that kill related strains

Colonies of sixty-five filamentous cyanobacteria were screened for the production of temperate phages and/or antibiotics on solid medium. None of them was observed to release phages. However, seven N2-fixing strains were found to produce antibiotics very active against other cyanobacteria. The antibiotic produced by Nostoc sp. 78-11A-E represents a bacteriocin of low molecular weight. Nostoc sp. ATCC 29132 appears to secrete, together with an antibiotic, a protein that inhibits its action.