Temperature-Regulated Formation of Mycelial Mat-Like Biofilms by Legionella pneumophila

Abstract

Fifty strains representing 38 species of the genus Legionella were examined for biofilm formation on glass, polystyrene, and polypropylene surfaces in static cultures at 25°C, 37°C, and 42°C. Strains of Legionella pneumophila, the most common causative agent of Legionnaires' disease, were found to have the highest ability to form biofilms among the test strains. The quantity, rate of formation, and adherence stability of L. pneumophila biofilms showed considerable dependence on both temperature and surface material. Glass and polystyrene surfaces gave between two-to sevenfold-higher yields of biofilms at 37°C or 42°C than at 25°C; conversely, polypropylene surface had between 2 to 16 times higher yields at 25°C than at 37°C or 42°C. On glass surfaces, the biofilms were formed faster but attached less stably at 37°C or 42°C than at 25°C. Both scanning electron microscopy and confocal laser scanning microscopy revealed that biofilms formed at 37°C or 42°C were mycelial mat like and were composed of filamentous cells, while at 25°C, cells were rod shaped. Planktonic cells outside of biofilms or in shaken liquid cultures were rod shaped. Notably, the filamentous cells were found to be multinucleate and lacking septa, but a recA null mutant of L. pneumophila was unaffected in its temperature-regulated filamentation within biofilms. Our data also showed that filamentous cells were able to rapidly give rise to a large number of short rods in a fresh liquid culture at 37°C. The possibility of this biofilm to represent a novel strategy by L. pneumophila to compete for proliferation among the environmental microbiota is discussed.

Transcriptional profiling of Legionella pneumophila biofilm cells and the influence of iron on biofilm formation

“…Our study has revealed that biofilm formed by L. pneumophila is more consistent at 20 u C than at 37 or 42 u C. Piao et al (2006) also reported that the L. pneumophila biofilms with structural features typical of biofilms (i.e. pillar-and mushroom-like structures) formed at 25 u C remained more stably attached than filamentous, mycelial-mat-like biofilms formed at 37 and 42 u C. Also, Mampel et al (2006) reported that biofilm formation at 37 u C was 30 % lower than at 23 and 30 u C. Furthermore, we have shown that adhesion is highest for late stationary phase cells.…”

“…Recently, two different studies have investigated the ability of L. pneumophila to form monospecies biofilms. Piao et al (2006) tested different materials and temperatures for biofilm formation, reporting that on glass and polystyrene biofilms were formed more slowly at 25 u C than at 37 or 42 u C but that they remained more stably attached at 25 u C. At 25 u C biofilms possessed structural features typical of biofilms reported previously (i.e. pillar-and mushroom-like structures) whereas at 37 u C, filamentous, mycelial-mat-like biofilms were the structures observed.…”

“…Although these models do not reflect the complexity found in natural environmental biofilms, monospecies biofilms were the first step towards understanding adaptation to the sessile lifestyle for many bacteria, including two recent studies on L. pneumophila (Mampel et al, 2006;Piao et al, 2006). These models pave the way for the study of complicated microbial interactions and have proven to be useful for assessing the gene expression profile of sessile cells even if the different cell types present within a biofilm cannot be analysed independently by this approach (Schembri et al, 2003;Beloin et al, 2004;Waite et al, 2005;Whiteley et al, 2001).…”

A Sporulation Factor Is Involved in the Morphological Change of Clostridium perfringens Biofilms in Response to Temperature

“…Temperature is an important factor for biofilm formation, and numerous studies have indicated that temperature affects the amount of biofilm in Escherichia coli, Legionella pneumophila, Listeria monocytogenes, and B. cereus (41)(42)(43)(44). In C. perfringens, temperature drastically affects biofilm morphology, potentially reflecting the temperature-dependent regulation of EPS production and cell adhesion.…”

Detecção de bactérias do gênero Legionella em amostras de água de sistemas de ar condicionado<a href="#endereco"></a>

“…Relatos encontrados na literatura consultada sugerem associação entre a presença de biofilme e a presença do gênero Legionella. [20][21][22] No presente estudo, entretanto, não foi possível demonstrar essa relação dado o número de amostras positivas para a presença de Legionella sp. e a grande variação na concentração de bactérias heterotróficas nas amostras analisadas.…”