https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

Antibiotics have always been considered one of the wonder discoveries of the 20th century. This is true, but the real wonder is the rise of antibiotic resistance in hospitals, communities, and the environment concomitant with their use. The extraordinary genetic capacities of microbes have benefitted from man's overuse of antibiotics to exploit every source of resistance genes and every means of horizontal gene transmission to develop multiple mechanisms of resistance for each and every antibiotic introduced into practice clinically, agriculturally, or otherwise. This review presents the salient aspects of antibiotic resistance development over the past half-century, with the oft-restated conclusion that it is time to act. To achieve complete restitution of therapeutic applications of antibiotics, there is a need for more information on the role of environmental microbiomes in the rise of antibiotic resistance. In particular, creative approaches to the discovery of novel antibiotics and their expedited and controlled introduction to therapy are obligatory.

Origins and Evolution of Antibiotic Resistance

The effects of initial nitrogen and lignin contents of six species of hardwood leaves on their decomposition dynamics were studied at the Hubbard Brook Experimental Forest. Rate con- stants (k) for annual leaf mass loss ranged from -0.08 to -0.47. The rate constants (k) had a negative linear correlation (r2 = .89) with the ratio of initial lignin concentration to initial nitrogen concentra- tion. Decomposition dynamics of the litter materials were described by inverse linear relationships between the percentage of original mass remaining and the nitrogen concentration in the residual material. Initial lignin concentration was highly correlated (r2 = .93) with the slope of the inverse linear relationship for each of the litter types.

Nitrogen and Lignin Control of Hardwood Leaf Litter Decomposition Dynamics

Metagenomics (also referred to as environmental and community genomics) is the genomic analysis of microorganisms by direct extraction and cloning of DNA from an assemblage of microorganisms. The development of metagenomics stemmed from the ineluctable evidence that as-yet-uncultured microorganisms represent the vast majority of organisms in most environments on earth. This evidence was derived from analyses of 16S rRNA gene sequences amplified directly from the environment, an approach that avoided the bias imposed by culturing and led to the discovery of vast new lineages of microbial life. Although the portrait of the microbial world was revolutionized by analysis of 16S rRNA genes, such studies yielded only a phylogenetic description of community membership, providing little insight into the genetics, physiology, and biochemistry of the members. Metagenomics provides a second tier of technical innovation that facilitates study of the physiology and ecology of environmental microorganisms. Novel genes and gene products discovered through metagenomics include the first bacteriorhodopsin of bacterial origin; novel small molecules with antimicrobial activity; and new members of families of known proteins, such as an Na+(Li+)/H+ antiporter, RecA, DNA polymerase, and antibiotic resistance determinants. Reassembly of multiple genomes has provided insight into energy and nutrient cycling within the community, genome structure, gene function, population genetics and microheterogeneity, and lateral gene transfer among members of an uncultured community. The application of metagenomic sequence information will facilitate the design of better culturing strategies to link genomic analysis with pure culture studies.

Metagenomics: Application of Genomics to Uncultured Microorganisms

Instead of containing stable and chemically unique ‘humic substances’, as has been widely accepted, soil organic matter is a mixture of progressively decomposing organic compounds; this has broad implications for soil science and its applications. The exchange of nutrients, energy and carbon between soil organic matter, the soil environment, aquatic systems and the atmosphere is important for agricultural productivity, water quality and climate. Long-standing theory suggests that soil organic matter is composed of inherently stable and chemically unique compounds. Here we argue that the available evidence does not support the formation of large-molecular-size and persistent ‘humic substances’ in soils. Instead, soil organic matter is a continuum of progressively decomposing organic compounds. We discuss implications of this view of the nature of soil organic matter for aquatic health, soil carbon–climate interactions and land management. Soil organic matter contains a large portion of the world's carbon and plays an important role in maintaining productive soils and water quality. Nevertheless, a consensus on the nature of soil organic matter is lacking. Johannes Lehmann and Markus Kleber argue that soil organic matter should no longer be seen as large and persistent, chemically unique substances, but as a continuum of progressively decomposing organic compounds.

The contentious nature of soil organic matter

SummaryA new antibacterial substance, designated as streptomycin, was isolated from two strains of an actinomyces related to an organism described as Actinomyces griseus. This substance resembles s...

Streptomycin, a Substance Exhibiting Antibiotic Activity Against Gram-Positive and Gram-Negative Bacteria.∗†:

Since the publication by one of us (Waksman, 1940) of a system of classification of actinomycetes, considerable criticism was expressed in regard to the designation and position of the anaerobic pathogenic species, the cause of common actinomycosis in man and \"lumpy jaw\" in cattle. This type of organism was placed in the genus Cohnistreptothrix Pinoy, the generic name Actinomyces being reserved for the aerobic species forming aerial mycelium-bearing spores. This could be justified on the ground that the organism seen by Harz was so poorly described and illustrated that it is unrecognizable by present day standards, and that therefore a new name could well be applied to the organism of actinomycosis in cattle; that further the name Actinomyces was the first one applied to cultivated, aerobic, spore-forming species which can be recognized by present day standards. This has been the attitude of a number of recent medical mycologists, especially the Italian workers (Ciferri and RedaeUi, 1929; Baldacci, 1939). Critics of Waksman's classification have, however, maintained that while Harz' description of his organism is perhaps vague, there is no question concerning the nature of the disease he studied, and that the chances are overwhelmingly in favor of his having actually observed the anaerobic pathogenic filamentous organism first described by Israel. Further, under the Botanical Code, the name Actinomyces must be applied either to the organism of \"lumpy jaw\" or not used at all. This problem became particularly significant in view of the need for the revision of the Actinomycetaes for the sixth edition of Bergey's Manual which is being undertaken by the authors of this paper. We have been reluctant to deviate from Waksman's classification because we have felt that to abandon the name Actinomyces for the large group of aerobic spore-forming species would cause more confusion than to adopt the name Cohnistreptothrix, already in wide usage, for the anaerobic, pathogenic species. It appears, however, that under the code we have no such choice open to us. We believe that, to avoid similar dilemmas in the future, the code should be modified to permit generic names in wide usage based upon type cultures to have priority over names based merely upon morphologic descriptions.

The Nomenclature and Classification of the Actinomycetes.

THE demonstration of Schloesing and Muntz in 1877 that in sewage beds ammonia is converted into nitrate by biological agencies, and the further demonstration by Warington that two species of bacteria are involved, followed by their isolation by Winogradsky, turned the thoughts of soil investigators towards the biological aspect of soil fertility.Principles of Soil Microbiology.By Prof. Selman A. Waksman. Pp. xxviii + 897 + 19 plates. (London: Baillière, Tindall and Cox, 1927.) 45s. net.

Principles of Soil Microbiology

The Actinomycetes. A summary of current knowledge.

I would like to call your attention to an error that crept into the paper on neomycin by Waksman and Lechevalier (Science, March 25). On page 307, right column, lines 1, 8, and 9, the letter μ shou...

https://science.sciencemag.org/content/sci/109/2830/305.full.pdf

Selman A. Waksman

Papers

Streptomycin, a Substance Exhibiting Antibiotic Activity Against Gram-Positive and Gram-Negative Bacteria.∗†:

The Nomenclature and Classification of the Actinomycetes.

Principles of Soil Microbiology

The Actinomycetes. A summary of current knowledge.

Neomycin, a New Antibiotic Active against Streptomycin-Resistant Bacteria, including Tuberculosis Organisms.