Escherichia coli strain SPA O converts methionine to ethylene by an inducible enzyme system. L-Cysteine, L-homocysteine, methionine derivatives and the sulphur-containing analogues of L-methionine also act as precursors of ethylene. Ethylene is produced by cell suspensions only in the presence of air; cell-free preparations can produce ethylene aerobically and anaerobically, but the extent to which they do so depends on the mode of culture growth. Light stimulates ethylene production by cell suspensions and its presence is essential for production by cell-free preparations. The kinetics of ethylene biogenesis and its pH and temperature optima suggest that ethylene is a secondary metabolite.
The concept of biomimetics stems from the realization that microbes, plants, and animals have been continuously evolving to cope with environmental and other challenges. Janine Benyus has pointed out that there are two types of biomimetics: forward biomimetics and reverse biomimetics. The earliest recorded attempts at biomimicry relate to manned flight. Percy Shaw's invention of the reflective road studs, more commonly known as 'catseyes', has saved the lives of thousands of road users by lighting the way along roads in the dark. An early commercial product that truly was inspired by nature is the hook and loop fastener i.e. Velcro. The inventor was the Swiss engineer, George de Mestral. He conceived a linear piece of material with hooks that would stick to any rough material. That is, a simple fastener that, unlike a zip fastener or 'hooks and eyes', did not require two surfaces to be lined up precisely.
The replication of M-13 in a strain of Escherichia coli with a thermosensitive lesion in deoxyribonucleic acid synthesis was studied. M-13 failed to replicate at the restrictive temperature, even when the parental replicative form was allowed to form at the permissive temperature. When cells which were actively producing phage at the permissive temperature were shifted to the restrictive temperature, phage production continued. The incorporation of radioactive label into phage particles at 42 C indicated that continued single-strand synthesis was unaffected by the lesion in the host cell.
Microbiology Society journals contain high-quality research papers and topical review articles. We are a not-for-profit publisher and we support and invest in the microbiology community, to the benefit of everyone. This supports our principal goal to develop, expand and strengthen the networks available to our members so that they can generate new knowledge about microbes and ensure that it is shared with other communities.
Summary: During growth of Escherichia coli strain SPA o in the presence of methionine, an intermediate accumulates in the medium. This intermediate reacts with 2,4-dinitro-phenylhydrazine, and can be degraded to ethylene either enzymically or photo-chemically, the latter being stimulated by the addition of a flavin. The pH optimum for the photochemical degradation of this intermediate and 2-keto-4-methylthio-butyric acid (KMBA) is pH 3 whereas the optimum for methional is pH 6. The enzyme which converts the intermediate to ethylene also converts KMBA to ethylene and has many of the properties of a peroxidase including inhibition by catalase, cyanide, azide and anaerobiosis. The enzyme which synthesizes the intermediate is not known but requires oxygen and pyridoxal phosphate. A pathway for ethylene biosynthesis is proposed in which methionine is converted to KMBA which can be degraded either by peroxidase or in a flavin-mediated photochemical reaction. Its relevance to the properties of other ethylene-producing bacteria and to the proposed pathway of ethylene release by higher plants is discussed.
Microbiology Society journals contain high-quality research papers and topical review articles. We are a not-for-profit publisher and we support and invest in the microbiology community, to the benefit of everyone. This supports our principal goal to develop, expand and strengthen the networks available to our members so that they can generate new knowledge about microbes and ensure that it is shared with other communities.
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