Starvation can diversify the population structure and virulence strategies of an environmentally transmitting fish pathogen

BMC Microbiology

E Tellervo Valtonen²  Heidi M T Kunttu²  Lotta-Riina Sundberg¹ 

[1] Centre of Excellence in Biological Interactions, University of Jyväskylä, Po box 35, FI-40014 Jyväskylä, Finland;Department of Biological and Environmental Science, University of Jyväskylä, Po box 35, FI-40014 Jyväskylä, Finland

关键词: Virulence;    Transmission;    Trade-off;    Starvation;    Flavobacterium columnare;   

Others  :  1141649
DOI  :  10.1186/1471-2180-14-67

 received in 2013-12-18, accepted in 2014-03-10,  发布年份 2014

【 摘 要 】

Background

Generalist bacterial pathogens, with the ability for environmental survival and growth, often face variable conditions during their outside-host period. Abiotic factors (such as nutrient deprivation) act as selection pressures for bacterial characteristics, but their effect on virulence is not entirely understood. “Sit and wait” hypothesis expects that long outside-host survival selects for increased virulence, but maintaining virulence in the absence of hosts is generally expected to be costly if active investments are needed. We analysed how long term starvation influences bacterial population structure and virulence of an environmentally transmitting fish pathogen Flavobacterium columnare.

Results

F. columnare populations in distilled water and in lake water were monitored for 5 months. During the experiment, the population structure of F. columnare diversified by rough and soft colony morphotypes appearing among the ancestral rhizoid ones. After 5 months starvation in lake water, the virulence of the starved and ancestral bacterial isolates was tested. The starved rhizoid isolates had significantly higher virulence than the ancestral rhizoid, whereas the virulence of the rough isolates was low.

Conclusions

We suggest that F. columnare population diversification is an adaptation to tolerate unpredictable environment, but may also have other biological significance. Maintaining and increasing virulence ensures efficient invasion into the host especially under circumstances when the host density is low or the outside-host period is long. Changing from rhizoid into a rough morphotype has trade-offs in making bacteria less virulent and unable to exploit the host, but may ensure bacterial survival under unpredictable conditions. Our study gives an example how abiotic selection can diversify virulence of environmentally transmitting bacterial pathogen.

【 授权许可】

   
2014 Sundberg et al.; licensee BioMed Central Ltd.

【 图 表 】

Figure 1.

Figure 2.

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