Heterotrophic bacteria of the freshwater neuston and their ability to act as plasmid recipients under nutrient deprived conditions

Abstract

Significantly higher numbers of Gram-negative heterotrophic bacteria were present at the air-water interface (neston) of freshwater lakes than in the bulk water. Neuston bacteria were distinguished as a population distinct from bacteria in the bulk water by a higher incidence of pigmented colony types and significantly greater levels of multiple resistance to antibiotics and heavy metals. The incidence of plasmids in 236 neuston and 229 bulk water strains were similar (14 and 16.2%, respectively). Nine of 168 plasmid-free strains and 2 of 14 plasmid carrying strains, isolated from both bulk water and neuston, acted as recipients of plasmid R68.45 in plate matings with aPseudomonas aeruginosa donor strain PAO4032 at 21°C, but at frequencies below that of matings with a restriction-minus recipient strain ofP. aeruginosa, strain PAO1168. In a model system composed of nutrient-free synthetic lake water, plasmid R68.45 was shown to transfer betweenP. aeruginosa strains at frequencies between 10(-3) and 10(-5). Transconjugants were detected about 100 times more frequently at the interface than in the bulk water, which in part reflected a greater enrichment of the donor at this site. None of the aquatic isolates were able to act as recipients of plasmid R68.45 in this model system with strain PAO4032 as donor. The results suggest that under nutrient deprived conditions, the spread of plasmid R68.45 and similar plasmids by lateral transfer into this particular aquatic population would be a rare event.

Increased Transfer of a Multidrug Resistance Plasmid in Escherichia coli Biofilms at the Air-Liquid Interface

“…Examples of such natural hot spots are the scum layers on standing bodies of water and the surface microlayers (SML) in lakes and oceans (17,28). Our postulate is corroborated by various studies that observed plasmid transfer or detected plasmids in such natural ecosystems (4,19,20,32,38,44). There are multiple possible explanations for the observed increased plasmid transfer at the air-liquid interface compared to that in submerged biofilms, and they likely involve a combination of the physical properties of the environment as well as the physiological state of the cells.…”

Method for Collecting Air-Water Interface Microbes Suitable for Subsequent Microscopy and Molecular Analysis in both Research and Teaching Laboratories

“…5B to D) indicate that a freshwaterenvironment AWI bacterial community was quite distinct from the subsurface community directly beneath it. Other less-specific collection methods for freshwater (11) and marine (16) surface microorganisms have provided qualitative data that have resulted in conclusions similar to those found in the present study but with no correlative microscopic data.…”

RETRACTED: Occurrence and Seasonal Distribution of Antibiotic Resistance Heterotrophic Bacteria and Physico-chemical Characteristics of Muthupettai Mangrove Environment, Southeast Coast of India

“…This is why many studies have been recently carried out to determine the distribution of antibiotic resistance bacteria in freshwater basins, estuaries, municipal drinking water and sewage waters (Niemi et al, 1983;Calomiris et al, 1984;Jones et al, 1991;Herwig et al, 1997;Ash et al, 2002;Mudryk, 2002). However, relatively very few studies on antibiotic resistance bacteria in marine water (Nair et al, 1992;Mudryk and Skorczewski, 1998) and only very less studies have been undertaken in dynamic ecosystem such as mangrove environment.…”