Evaluation of the interactions between the marine bacterium Pseudomonas fluorescens and the microalga Isochrysis galbana
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ORIGINAL PAPER
Evaluation of the interactions between the marine bacterium Pseudomonas fluorescens and the microalga Isochrysis galbana in simulated ballast tank environment Aline da Silva Câmara1,2 · Lohengrin Dias de Almeida Fernandes1,2 Received: 22 May 2018 / Revised: 11 August 2018 / Accepted: 29 August 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018
Abstract To evaluate the impacts of the interaction between bacteria and microalgae has been the object of study by many research groups around the world. However, little is known about the interference that pigments produced by bacteria, such as the pyoverdine siderophore, can cause to microalgae like Isochrysis galbana. Pyoverdine is a fluorochrome produced by certain Pseudomonas strains, such as P. fluorescens, which plays a role in capturing and transporting iron ions from the environment to the cell. Unlike the oceans where Fe concentrations are extremely low ( 530 nm). The total number of events recorded per sample was limited to 50,000, in a flow not exceeding 1000 events according to Gasol and Moran (2015). For quantification of the microalgae population growth, Neubauer chamber was used in inverted epifluorescence microscopy (Olympus BX71). Quantification of chlorophyll in alive was evaluated by means of a Turner AquaFluor fluorimeter. The potential effect of the growth of P. fluorescens bacteria on the growth of I. galbana microalgae was evaluated by means of a Variance Analysis (ANOVA) with repeated measures in time. The factors Light (Dark vs Photoperiod 12:12) and Interaction (Microalgae and Combined Bacteria vs Controls) were included, in intervals of 12 h up to the total of 84 h. The calculations were performed in StatSoft Statistical 7.0 with probability of significance established in 0.5.
Fig. 1 Population growth of Pseudomonas fluorescens (cell mL) over time (84 h). The graphs a and b show the temporal variation of the counting of P. fluorescens control maintained in the light (a) and in
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Archives of Microbiology
Results and discussion Pseudomonas fluorescens: bacterial quantification The cell density of the bacteria was maintained throughout the experiment at a linear growth between 1 × 104 and 5 × 104 cells mL−1. No interference of light was observed on cell development, since growth was similar under all conditions. The presence of microalgae also did not affect the growth of bacteria (Fig. 1).
Analysis of cytometry and spectrophotometry: pyoverdine (PVD) The suspension concentration of pyoverdine was intensified after the first 12 h of the experiment, after the acclimation phase of the bacterial cells (Fig. 2). Thereafter, there was a second peak in the PVD concentration in about 60 h. The PVD level of the bacterial samples in the control or in interaction with the microalgae (Fig. 2a, b) varied between 10 and 80 µM.
the dark (b) The graphs c and d show the temporal variation of the counting of P. fluorescens in interaction with I. galbana in the light (c) and in the dark (d)
Archives of Microbiology
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