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Different antibiotic resistance of neustonic and planktonic bacteria in a freshwater coastal lake : implication for strain selection

100%

Skórczewski P. , Mudryk Z.

Polish Journal of Ecology

2012

tom Vol. 60, nr 1

153-162

Antibiotic resistance of bacteria was observed in various aquatic environments including seas, rivers, lakes, coastal areas, surface water and sediments. The increased implementation of antibiotics into these environments through medical therapy, agriculture and animal husbandry has resulted in new selective pressures on natural bacterial aquatic populations. Antibiotic resistance of heterotrophic bacteria isolated from the surface microlayer and subsurface water of freshwater coastal polymictic and low-productive lake was studied. Antibiotic resistance was determined by the single disc diffusion method. The resistance level of bacteria to various antibiotics differed considerably. Bacteria were most resistant to ampicillin, ciprofloxacin, clindamycin, erythromycin and penicillin. Majority of bacterial strains showed resistance to 4.6 out of 18 antibiotics tested. As a rule, neustonic bacteria (antibiotic resistance index, ARI 0.44) were more resistant to the studied antibiotics than planktonic bacteria (ARI 0.32). 70-90% of neustonic bacteria were resistant to ampicillin, clindamycin and erythromycin, 60-70% of planktonic bacteria were resistant to ampicillin, ciprofloxacin and penicillin. Differences between pigmented and non-pigmented bacteria in their resistance to the tested antibiotics were observed. Above 40% of achromogenic bacterial strains were resistant to ampicillin, clindamycin and penicillin. Among bacterial strains characterised by their ability to synthesize carotenoids, more than 30% was resistant to ampicillin and ciprofloxacin. Bacterial resistance level to antibiotics depended on their chemical structure. Bacteria isolated from study lake were most resistant to quinolones and lincosamides while they were most susceptible to tetracyclines and aminoglycosides. Results presented in this paper indicate that antibiotics are a significant selection factor and probably play an important role in regulating the composition of bacterial communities in aquatic ecosystems. Adaptive responses of bacterial communities to several antibiotics observed in the present study may have possible implications for the public health.

UV Radiation Impact on Enzymatic and Respiratory Activity of Neustonic and Planktonic Bacteria

100%

Walczak M. , Burkowska A.

2011

tom Vol. 18, nr 5-6

827-833

The surveys were carried out in the pelagic zone of Brzezno lake (the Tuchola Forest). Water samples were collected from the surface microlayer and the subsurface water. The surveys covered respiratory activity of bacteria, using a measurement system OxiTop Control. Also, general activity of hydrolytic enzymes was estimated measuring rates of fluorescein release from fluorescein diacetate. The research was conducted in two experimental layouts: with and without humic substances. Conducted surveys proved substantially lower respiratory and hydrolytic activity of bacteria influenced by UVB radiation compared with bacteria without UVB radiation. The experiments did not prove unambiguous protective operation of HS – only for selected strains with bacteria subjected to UVB radiation in presence of HS demonstrated lower decrease of respiratory and hydrolytic activity.

Badania prowadzono w dwóch układach doświadczalnych: bez substancji humusowych (SH) i w obecności tych substancji. W wyniku przeprowadzonych badań stwierdzono zdecydowanie niższą aktywność oddechow ą i hydrolityczną bakterii po naświetleniu UVB, w porównaniu z bakteriami nie naświetlonymi. Nie stwierdzono jednoznacznie ochronnego działania SH, jedynie w przypadku niektórych szczepów naświetlanie bakterii UVB w obecności SH powodowało mniejszy spadek aktywności oddechowej i hydrolitycznej.