Antibiotics phytotoxicity

The application of various antibiotics such as rifampicin/tetracycline (63), cefatoxime/trimethoprim (64), or bacteriostatic compounds such as Micropur (Roth, Karlsruhe, Germany) (65) used for root pretreatment or added to collection media is another strategy to prevent biodegradation during root exudate collection. However, depending on dosage and plant species, also phytotoxic effects of antibiotics have been reported (Table 3). Antibiotics in the soil environment... 

Rationale. Microorganisms were isolated from soil and screened for toxin production according to the scheme in Figure 1. Some of the organisms causing strong inhibition on solid medium were tested for toxin production in liquid medium. Liquid culture will be required to obtain large amounts of material for commercial production of herbicides, however, the ability to produce toxins on solid medium does not necessarily imply toxin production in broth (34). Cyclo-heximide, a phytotoxic but relatively nonspecific antibiotic with little value as a herbicide, is produced by many actinomycetes. Liquid cultures were tested for cycloheximide to determine whether it caused the observed toxicity. 

They are well known for their biological importance as hormones, antibiotics, toxins, ion-transport regulators, antivirals, phytotoxic compounds, and so on. °... 

The myxobacterium Chondromyces crocatus contains the novel chondrochlo-rens A (831) and B (832) (879). A marine Streptomyces species has afforded the manumycin antibiotics chinikomycins A (833) and B (834) (880). While inactive in antiviral, antimicrobial, and phytotoxicity screens, these chinikomycins display some cytotoxic activity. 

Since the era of the antibiotics, no new compounds have been developed for the control of diseases caused by phytopathogenic prokaryotes. Even these antibiotics are not used in many areas of the world because of governmental restrictions that prevent their use on agricultural crops. Problems with resistance are reducing the usefulness of the antibiotics even further. Copper compounds, which are generally less effective than the antibiotics, are the main compounds available to control bacterial incited diseases. Unfortunately, copper compounds are phytotoxic to many crops. 

Some plant pathogenic bacteria and their phytotoxins have been screened in bioassays that monitor the effects of their toxins (antibiotic and phytotoxic) on other sensitive bacteria. For example, several fluorescent Pseudomonas syringae pvs. produce extracellular phytotoxins.76,106,116 Tabtoxin is produced by P. syringae pv. tabaci and pv. coronafacines, and this natural product inhibits glutamine synthetase.34,46,116 Phaseolotoxin, produced by P. syringae pv. phaseolicola... 

Blasticidin S. Blasticidin S is the first successful agricultural antibiotic developed in Japan. It was isolated from the culture filtrates of Streptomyces griseochromogenes by Takeuchi et al. (7), and the potent curative effect of blasticidin S on rice blast was found by Misato et al. (8) Thereafter the benzyl-aminobenzene sulfonate of blasticidin S was reported to be least phytotoxic to the host plant without reducing antifungal activity against Pyricularia oryzae, the pathogen of rice blast (9), and... 

Several polyacetylenes have antibiotic properties and some are phytotoxic. Agrocybin (4.105), originally isolated from Agrocybe dura, is also formed by the fairy-ring fungus, Marasmius oreades, and it may be responsible for the death of grass. Their production as extracellular mycelial metabolites may thus facilitate the spread of the mycelium in a hostile environment. The dry-rot... 

Antibiotics can also be used for weed control. Monsanto isolated one from a Streptomyces culture (11.57) that showed over 90% phytotoxicity to several broad-leaved weeds, without hurting wheat at a level of 7 g/acre.236... 

Most of the antibiotics are unstable compounds — they are rapidly degraded by abiotic and biotic factors into biologically inactive compounds, so that they leave little or no residue. Usually no problems are caused from the point of view of environmental protection and, in any case, they are applied to plants in relatively small concentrations. However, because of their rapid degradation, their effects decrease considerably more rapidly than those of conventional fungicides, thus the checking of their efficiency is very important. In many cases, their phytotoxicity is considerable, which limits their application. Another limiting factor is the relatively rapid development of resistance to antibiotics. Antibiotics have not as yet shown any fundamental effect against viral diseases. 

Polyene antibiotics are not phytotoxic. In spite of this they are not widely used, mainly because of their instability. After application they are rapidly degraded by oxidation on the plant surfaces. Although these antibiotics have a systemic action, when absorbed through the roots they lose their antifungal activity in the plant, probably because they are bound by certain plant components and are thus inactivated (Oort and Dekker 1960). 

Validamycins are not phytotoxic, nor are they toxic to mammals the acute ld,o for rats is higher than 20000 mg/kg. In three-moth toxicity tests no pathological effects were produced in any of the organs of mice or rats (Onishi and Miyaji, 1973). These antibiotics are not hazardous to fish or to bees or other beneficial insects. In... 

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