Spatial scales of competition and a growth-motility tradeoff interact to determine bacterial coexistence

The coexistence of competing species is a long-lasting puzzle in evolutionary ecology research. Despite abundant experimental evidence showing that the opportunity for coexistence decreases as niche overlap increases between species, bacterial species and strains competing for the same resources are commonly found across diverse spatially heterogeneous habitats. We thus hypothesized that the spatial scale of competition may play a key role in determining bacterial coexistence, and interact with other mechanisms that promote coexistence, including a growth-motility tradeoff. To test this hypothesis, we let two Pseudomonas putida strains compete at local and regional scales by inoculating them either in a mixed droplet or in separate droplets in the same Petri dish, respectively. We also created conditions that allow the bacterial strains to disperse across abiotic or fungal hyphae networks. We found that competition at the local scale led to competitive exclusion while regional competition promoted coexistence. When competing in the presence of dispersal networks, the growth-motility tradeoff promoted coexistence only when the strains were inoculated in separate droplets. Our results provide a mechanism by which existing laboratory data suggesting competitive exclusion at a local scale is reconciled with the widespread coexistence of competing bacterial strains in complex natural environments with dispersal.

Xanthoepocin, a photolabile antibiotic of Penicillium ochrochloron CBS 123823 with high activity against multiresistant gram-positive bacteria

Background With the steady increase of antibiotic resistance, several strategies have been proposed in the scientific community to overcome the crisis. One of many successful strategies is the re-evaluation of known compounds, which have been early discarded out of the pipeline, with state-of-the-art know-how. Xanthoepocin, a polyketide widespread among the genus Penicillium with an interesting bioactivity spectrum against gram-positive bacteria, is such a discarded antibiotic. The purpose of this work was to (i) isolate larger quantities of this metabolite and chemically re-evaluate it with modern technology, (ii) to explore which factors lead to xanthoepocin biosynthesis in P. ochrochloron, and (iii) to test if it is beside its known activity against methicillin-resistant Staphylococcus aureus (MRSA), also active against linezolid and vancomycin-resistant Enterococcus faecium (LVRE)—a very problematic resistant bacterium which is currently on the rise. Results In this work, we developed several new protocols to isolate, extract, and quantify xanthoepocin out of bioreactor batch and petri dish-grown mycelium of P. ochrochloron. The (photo)chemical re-evaluation with state-of-the-art techniques revealed that xanthoepocin is a photolabile molecule, which produces singlet oxygen under blue light irradiation. The intracellular xanthoepocin content, which was highest under ammonium-limited conditions, varied considerably with the applied irradiation conditions in petri dish and bioreactor batch cultures. Using light-protecting measures, we achieved MIC values against gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), which were up to 5 times lower than previously published. In addition, xanthoepocin was highly active against a clinical isolate of linezolid and vancomycin-resistant Enterococcus faecium (LVRE). Conclusions This interdisciplinary work underlines that the re-evaluation of known compounds with state-of-the-art techniques is an important strategy in the combat against multiresistant bacteria and that light is a crucial factor on many levels that needs to receive more attention. With appropriate light protecting measures in the susceptibility tests, xanthoepocin proved to be a powerful antibiotic against MRSA and LVRE. Exploring the light response of other polyketides may be pivotal for re-introducing previously discarded metabolites into the antibiotic pipeline and to identify photosensitizers which might be used for (antimicrobial) photodynamic therapies.

Bradysia aff. impatiens and Bradysia aff. ocellaris in the semi-hydroponic strawberry production system in Southern Brazil

ABSTRACT: Soilless cultivation of strawberry is in expansion in Brazil due to factors like the reduction of phytosanitary problems and the possibility of extending the crop period, as well as the ergonometric facility for management of the culture. However, black fungus gnats (Sciaridae, Diptera) are ubiquitous pests in the greenhouse production system, causing direct and indirect damage to plants. ThIS study evaluated the occurrence of black fungus gnats species in semi-hydroponic cultivation of strawberry and to identify the species, as well as to describe the symptoms in infested plants. The research was developed in commercial productions of strawberry, in five municipalities (Arroio do Padre, Canguçu, Capão do Leão, Pelotas and Turuçu) during July to December 2017, where adult samples were collected twice a month, with petri dish traps containing water and neutral detergent placed inside the greenhouses between the plants. A total of 2030 adult gnats belonging to two species were collected. Bradysia aff. impatiens, accounted with 90.79% of the total, and Bradysia aff. ocellaris, accounted with 9.21%. In order to assist the correct determination of species, males of both species were identified and illustrated. With respect to the symptoms observed during the research, it was possible to verify since the wilted crown of plants to the death of plants, which were confirmed by the presence of larvae in the root system. As the occurrence of these insects is recent in strawberry, there is no pesticide registered in Brazil, so management strategies (cultural, physical, and sanitary) also are discussed.

A three-dimensional (3D) printing approach to fabricate an isolation chip for high throughput in situ cultivation of environmental microbes

The 3D-printed iChip version made from thermoplastics or photopolymers can isolate microbial populations of a peat swamp in situ with a population profile different from that isolated via the standard in vitro Petri dish cultivation method.

Breeding technique of Selenothrips rubrocinctus (Giard, 1901) (Thysanoptera: Thripidae) on roses leaflets

The development of adequate methods for maintaining populations of arthropod organisms in the laboratory has been a challenge due to the characteristics of each species. This work has aimed to define a method for breeding Selenothrips rubrocinctus (Giard, 1901) in rose leaflets in order to study this species in the laboratory. A condition which could maintain the leaflets turgor for a longer time was sought, in order to guarantee both the survival and multiplication of the insects, and less influence of abiotic factors. Four types of substrates were tested: a) a filter paper disk moistened with distilled water covering the bottom of a Petri dish and; b) a vegetable sponge moistened with distilled water surrounding the base of the leaflet; c) a potato, dextrose and agar (BDA) in a microcentrifuge tube surrounding the base of the leaflet; and d) hydrogel in a microcentrifuge tube surrounding the base of the leaflet. The filter paper moistened with distilled water allowed 65% of the leaflets to remain turgid over a 10-day period and was the most suitable substrate for thrips breeding. With the results at hand, we described S. rubrocinctus breeding in the laboratory. The adopted methodology provided the population density stability of the bred insects, as well as the obtainment of specimens of S. rubrocinctus in quantity and quality throughout the entire period of development of studies on the biology of the species.

Microbiological surveillance of air and contact surface of pubic transports with its correlation to human infection risks

Over past few years, people are giving more attention to air pollution and its effects on human health. Due to the high population density in Bangladesh, air pollution is a major issue in metropolitan areas, especially in Dhaka city. Present study aims to isolate air-borne microbes from the inside environment of public transport and different types of microbes that are frequently encountered by commuters when they touch the interior surfaces of vehicles used for public transport in Dhaka City. Atmospheric load of microorganisms was measured with petri dish which was kept open for 30 minutes in the sampling locations and swabs were taken from interior surfaces of vehicles. Air samples collected from both bus and railway stations showed a high atmospheric microbial count (total viable bacteria and total fungal count were 140 to 776 CFU/plate/30 min and 27 to 168 CFU/plate/30 min, respectively). A similar outcome was found after analysis of swab samples of the contact surfaces of the vehicles as well. A total of four bacterial pathogens were identified from the interior surfaces of the vehicle including Escherichia coli, Bacillus spp., Pseudomonas spp. and Vibrio spp. which are known to be associated with gastrointestinal tract infection. To manage and control the environmental health risks caused by air pathogens, an authorized governmental agency should do continuous monitoring of air quality to reduce the negative effects and impacts of air pathogens on human and animal health. This research has shown a great concern to health practitioners in developing countries because these are pathogens that are mostly resistant to the commonly available antibiotics used in the treatment of infection associated with these pathogens. Most importantly, we need to raise awareness among the public in order to reduce the load and spread of pathogenic bacteria in the environment. Stamford Journal of Microbiology, Vol.11 (1) 2021: 7-10

A rapid-prototyped moulding system towards optimised scalable fabrication of elastomeric microfluidic devices

3D printing and makerspace technologies are increasingly explored as alternative techniques to soft lithography for making microfluidic devices, and for their potential to segue towards scalable commercial fabrication. Here we considered the optimal application of current benchtop 3D printing for microfluidic device fabrication through the lens of lean manufacturing and present a straightforward but robust rapid prototyped moulding system that enables easy estimation of more precise quantities of polydimethylsiloxane (PDMS) required per device to reduce waste and importantly, making devices with better defined depths and volumes for (i) modelling gas exchange and (ii) fabrication consistency as required for quality-controlled production. We demonstrate that this low-cost moulding step can enable a 40 – 300% reduction in the amount of PDMS required for making individual devices compared to the established method of curing approximately 30 grams of PDMS prepolymer overlaid on a 4” silicon wafer master in a standard plastic petri dish. Other process optimisation techniques were also investigated and are recommended as readily implementable changes to current laboratory and foundry-level microfluidic device fabrication protocols for making devices either out of PDMS or other elastomers. Simple calculators are provided as a step towards more streamlined, software controlled and automated design-to-fabrication workflows for both custom and scalable lean manufacturing of microfluidic devices.