Vertical Distribution of Potentially Pathogenic Free‐Living Amoebae in Freshwater Lakes¹

Abstract

The vertical distribution of thermotolerant (37 degrees C and 45 degrees C) free-living amoebae (FLA) in warm monomictic lakes was determined in relation to the onset of thermal stratification and associated physical and chemical changes. The position of abiotic or biotic particulate layers in the water column was located by using a submersible horizontal beam transmissometer that measures attenuance, or the absorption and scattering of light by particulates in the water column. During mixis, the vertical distribution of amoebae was sporadic with significant numbers of FLA only occurring in clay layers caused by runoff after heavy rains. With the onset of thermal stratification in the lakes, phytoplankton layers began to form. Few amoebae were isolated from layers containing flagellated phytoplankton; however, significant (P less than 0.005) numbers of FLA were isolated from two particulate layers dominated by the filamentous blue-green algae Aphanizomenon and Lyngbya, respectively. By late June, a persistent detrital or decomposition layer formed in the lower metalimnion, as well as a hypolimnetic iron layer where the Fe2+ state was predominant. In this midsummer period, 13 Naegleria fowleri were isolated, with three from the detrital layer and seven from the iron layer. The presence of attenuation zones was found to be the best indicator of the vertical distribution of FLA in the water column, and such layers represent an important, previously undescribed habitat for potentially pathogenic FLA.

Naegleria fowleri after 50 years: is it a neglected pathogen?

“…However, this micro-organism has not been recovered from seawater, suggesting its sensitivity to elevated osmolarity. The vertical distribution of N. fowleri in water has been correlated with the presence of cyanobacteria and eubacteria; therefore, it is possible that the natural function of Naegleria genus is regulating bacterial populations (Kyle & Noblet, 1985). Additionally, the distribution of Naegleria has been associated with the concentrations of manganese and iron in the water column (Kyle & Noblet, 1985;Martinez-Castillo et al, 2015).…”

“…The vertical distribution of N. fowleri in water has been correlated with the presence of cyanobacteria and eubacteria; therefore, it is possible that the natural function of Naegleria genus is regulating bacterial populations (Kyle & Noblet, 1985). Additionally, the distribution of Naegleria has been associated with the concentrations of manganese and iron in the water column (Kyle & Noblet, 1985;Martinez-Castillo et al, 2015). N. fowleri is thermophilic and can survive temperatures of up to 45 C (Kyle & Noblet, 1987).…”

Sporadic high abundances of naked amoebae in Black Sea plankton

“…Highest abundances in the water column have been observed at the air/water interface (Davis 1976, Sieburth et al 1976, Davis et al 1978, Kyle & Noblet 1987, on the surfaces of microalgae or macroalgae (Cook et al 1974, Anderson 1977, Kyle & Noblet 1985, Rogerson 1991, or on suspended detrital aggregates (Caron et al 1982, Laybourn-Parry et al 1991, Rogerson & LaybournParry 1992, Arndt 1993. These surfaces presumably provide both substrata for amoeboid locomotion as well as foci for microaggregations of attached bacteria and other prey organisms.…”

“…In addition, the trophic activities of many of the species are inadequately defined, making it difficult to estimate the contribution of amoebae to energy and elemental flow in natural aquatic communities. Given these limitations, it is not surprising that much of the interest in free-living amoebae has been limited to potential human pathogens (Sawyer et al 1977, 1993, Daggett et al 1982, Kyle & Noblet 1985, Sawyer 1989.…”

The identification of Naegleria fowleri from water and soil samples by nested PCR

“…This pond is the result of runoff and contains less organic matter than other sampling sites tested. Kyle and Noblet (1985, 1987 noted that soil was the ideal habitat for free-living amebae and that runoff from rains introduced amebae into water. These investigators reported that significant increases in the numbers of Naegleria and Acanthamoeba were detected in surface water from a shallow water station after a major rainfall.…”