Abstract
BackgroundBacteriophages constitute a great threat to the activity of lactic acid bacteria used in industrial processes. Several factors can influence the infection cycle of bacteriophages. That is the case of the physiological state of host cells, which could produce inhibition or delay of the phage infection process. In the present work, the influence of Lactobacillus plantarum host cell starvation on phage B1 adsorption and propagation was investigated.ResultFirst, cell growth kinetics of L. plantarum ATCC 8014 were determined in MRS, limiting carbon (S-N), limiting nitrogen (S-C) and limiting carbon/nitrogen (S) broth. L. plantarum ATCC 8014 strain showed reduced growth rate under starvation conditions in comparison to the one obtained in MRS broth. Adsorption efficiencies of > 99 % were observed on the starved L. plantarum ATCC 8014 cells. Finally, the influence of cell starvation conditions in phage propagation was investigated through one-step growth curves. In this regard, production of phage progeny was studied when phage infection began before or after cell starvation. When bacterial cells were starved after phage infection, phage B1 was able to propagate in L. plantarum ATCC 8014 strain in a medium devoid of carbon source (S-N) but not when nitrogen (S-C broth) or nitrogen/carbon (S broth) sources were removed. However, addition of nitrogen and carbon/nitrogen compounds to starved infected cells caused the restoration of phage production. When bacterial cells were starved before phage infection, phage B1 propagated in either nitrogen or nitrogen/carbon starved cells only when the favorable conditions of culture (MRS) were used as a propagation medium. Regarding carbon starved cells, phage propagation in either MRS or S-N broth was evidenced.ConclusionsThese results demonstrated that phage B1 could propagate in host cells even in unfavorable culture conditions, becoming a hazardous source of phages that could disseminate to industrial environments.
Highlights
Bacteriophages constitute a great threat to the activity of lactic acid bacteria used in industrial processes
Bacterial growth kinetics When L. plantarum ATCC 8014 was subjected to starvation conditions, reduced growth rates were evidenced in comparison to those reached in Man Rogosa Sharpe (MRS) (Fig. 1)
Bacterial cells were able to grow until a OD560 value of 4.3+/−0.4 in MRS after 6 h at 37 °C whereas OD560 values of 3.0+/−0.2 and 2.8+/−0.3 were observed
Summary
Bacteriophages constitute a great threat to the activity of lactic acid bacteria used in industrial processes. That is the case of the physiological state of host cells, which could produce inhibition or delay of the phage infection process. Briggiler Marcó et al BMC Microbiology (2015) 15:273 As it is known, phage propagation depends on the physiology of the host cells [4,5,6]. Some authors reported the production of phage progeny even when the growth conditions of the bacterial strain were unfavorable [8,9,10] In this regard, it should be noted that the culture growth conditions in natural environments are quite different from those found in the laboratory, in which bacteria have all factors essential for a favorable growth [10]. Regarding LAB, the available information is only focused on the influence of bacterial metabolism (studied using starved cells) on some stages of the infective cycle (phage adsorption/DNA injection) in Lactobacillus casei [14, 15]
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