Oxidative foliar photo-necrosis produced by the bacteria Pseudomonas cedrina

BACKGROUND: Although bioactive metabolites capable of causing oxidative photo-necrosis in plant tissues have been identified in fungi, little is known about this type of mechanism in bacteria. These metabolites act as photosensitizers that generate reactive oxygen species (ROS) capable of causing damage to cells. In addition, these metabolites can pass into an energetically excited state when they receive some luminous stimulus, a condition in which they interact with other molecules present in the environment, such as molecular oxygen (O2), also known as triplet oxygen (3 O2), generating ROS. RESULTS: The suspension of the bacterial culture of Pseudomonas cedrina was shown to produce foliar necrosis in papaya leaves (Carica papaya L.) only in the presence of sunlight, which is evidence of photosensitizing mechanisms that generate singlet oxygen (1 O2). From the chemical study of extracts obtained from this bacteria, 3-(4-(2-carboxipropyl) phenyl) but-2-enoic acid (1) was isolated. This compound, in the presence of light and triplet oxygen (3 O2), was able to oxidize ergosterol to its peroxide, since it acted as a photosensitizer producing 1 O2, with which it was corroborated that a photosensitization reaction occurs, mechanism by which this bacterium could prove to cause oxidative foliar photo-necrosis. CONCLUSIONS: P. cedrina was able to induce oxidative foliar photo-necrosis because of its potential ability to produce photosensitizing metabolites that generate singlet oxygen in the plants it colonizes. Based on the above, it can be proposed that some bacteria can cause oxidative foliar photo-necrosis as an important mechanism in the pathogenesis of host species.

Antiproliferative activity of biomass extract from Pseudomonas cedrina

Background: The study of plant-associated microorganisms is very important in the discovery and development of bioactive compounds. Pseudomonas is a diverse genus of Gammaproteobacteria comprising more than 60 species capable of establishing themselves in many habitats, which include leaves and stems of many plants. There are reports of metabolites with diverse biological activity obtained from bacteria of this genus, and some of the metabolites have shown cytotoxic activity against cancer cell lines. Because of the high incidence of cancer, research in recent years has focused on obtaining new sources of active compounds that exhibit interesting pharmacodynamic and pharmacokinetic properties that lead to the development of new therapeutic agents. Results: A bacterial strain was isolated from tumors located in the stem of Pinus patula, and it was identified as Pseudomonas cedrina. Extracts from biomass and broth of P. cedrina were obtained with chloroform:methanol (1:1). Only biomass extracts exhibited antiproliferative activity against human tumor cell lines of cervix (HeLa), lung (A-549), and breast (HBL-100). In addition, a biomass extract from P. cedrina was fractioned by silica gel column chromatography and two diketopiperazines were isolated: cyclo-(L-Prolyl-L-Valine) and cyclo-(L-Leucyl-L-Proline). Conclusions: This is the first report on the association of P. cedrina with the stems of P. patula in Mexico and the antiproliferative activity of extracts from this species of bacteria against human solid tumor cell lines.

An unusual food plant for Cydia pomonella (Linnaeus) (Lepidoptera, Tortricidae) in Mexico

An unusual food plant for Cydia pomonella (Linnaeus) (Lepidoptera, Tortricidae) in Mexico. Larvae of Cydia pomonella (Linnaeus, 1758) were discovered on floral cones of Magnolia schiedeana (Schltdl, 1864) near the natural reserve of La Martinica, Veracruz, México. Magnolia represents an unusual host for this moth species, which is known throughout the world as the "codling moth", a serious pest of fruits of Rosaceae, especially apples. The larvae were identified using taxonomic keys, and identification was corroborated using molecular markers. Further sampling resulted in no additional larvae, hence, the observation was probably that of an ovipositional error by the female, and M. schiedeana is not at risk of attack by this important moth pest.