Identification and Characterization of a Novel Microalgal Strain from the Antofagasta Coast Tetraselmis marina AC16-MESO (Chlorophyta) for Biotechnological Applications

Abstract

The wide rocky coastline of the Antofagasta hosts an intertidal ecosystem in which the species that inhabit it are routinely exposed to a wide range of physical and chemical conditions and have therefore evolved to tolerate extremes. In the search for new species of potential biotechnological interest with adaptations to a wide range of environmental conditions, the isolation and characterization of microalgae from these ecosystems is of great interest. Here, a new microalgal strain, Tetraselmis marina AC16-MESO, is described, which was isolated from a biofilm collected on the intertidal rocks of the Antofagasta coast (23°36'57.2″ S, 70°23'33.8″ W). In addition to the morphological characterization, 18S and ITS sequence as well as ITS-2 secondary structure analysis revealed an identity of 99.76% and 100% with the species Tetraselmis marina, respectively. The analyses of the culture characteristics and biochemical content showed similarities with other strains that are frequently used in aquaculture, such as the species Tetraselmis suecica. In addition, it is tolerant of a wide range of salinities, thus allowing its culture in water of varying quality. On the other hand, added to these characteristics, the results of the improvement of the lipid content in stressful situations of salinity observed in this study, together with other antecedents such as the potential in bioremediation already published for this strain by the same research group, present a clear example of its biotechnological plasticity. It is noteworthy that this strain, due to its characteristics, allows easy collection of its biomass by decantation and, therefore, a more cost-efficient harvesting than for other microalgal strains. Therefore, this new strain of Tetraselmis marina, first report of this species in Chile, and its morphologically, molecularly and biochemically description, presents promising characteristics for its use in biotechnology and as feed for aquaculture.

Keywords: biodiversity; biotechnology; chlorophyta; identification.

Figure 1

Bright-field image (A,B) at 100× magnification and scanning electron micrograph (C,D) of the new microalgal strain T. marina AC16-MESO fixed to a mesh type substrate.

Figure 2

Secondary structure predictions for ITS-2 helix II (5′ to 3′). (A) T. marina AC16-MESO, T. marina IOAC331S, and T. marina CCMP898, (B) T. suecica and Tetraselmis sp. CCM-UDEC 109 (from Dichato), (C) T. subcondiformis and Tetraselmis sp. CCM-UDEC 134 (from Caldera), (D) Tetraselmis sp. CCM-UDEC 114 (from Coliumo), and (E) T. striata. Each colored interaction brings distinct properties to the intricate folding pattern. The red color emphasizes the robust G-C base pair interactions, crucial for both structural integrity and functional efficacy of the molecule. Blue color markings represent A-U interactions and green markings denote G-U interactions. The arrows indicate the supposed sites of RNA processing, and the boxes represent the compensatory base changes (CBCs).

Figure 3

Secondary structure predictions for ITS-2 helix III (5′ to 3′). (A) T. suecica, Tetraselmis sp. CCM-UDEC 109 (from Dichato), and Tetraselmis sp. CCM-UDEC 114 (from Coliumo), (B) T. marina AC16-MESO, T. marina IOAC331S and T. marina CCMP898. (C) T. subcondiformis and Tetraselmis sp. CCM-UDEC 134 (from Caldera), and (D) T. striata. The red color emphasizes the robust G-C base pair interactions, crucial for both structural integrity and functional efficacy of the molecule. Blue color markings represent A-U interactions and green markings denote G-U interactions. Arrows indicate potential RNA processing sites.

Figure 4

Phylogenetic tree based on 18S sequences of T. marina AC16-MESO and related microalgal species.

Figure 5

Phylogenetic tree based on ITS1-5.8S-ITS2 sequences of T. marina AC16-MESO and related microalgal species.

Figure 6

Growth curve of strain T. marina AC16-MESO over 20 days expressed as (A) cell density (cells × 10⁶/mL) and absorbance at 540 nm, and (B) biomass dry weight (g/L). Values represent the mean ± SD of three independent measurements in 2-liter reactors (n = 3). (C) The table shows the production (g L⁻¹ day⁻¹) during the exponential phase (day 2), early stationary phase (day 6), stationary phase (day 14), and late stationary phase (day 18). The arrows indicate the times for which biomass production was estimated.

Figure 7

Proximal analysis of T. marina AC16-MESO compared with reference biochemical analyses of N. gaditana and T. suecica. The reference strains were cultivated in the same facilities as the study strain and are part of the collection stock of the Applied Microbiology Unit, University of Antofagasta. Values represent the mean ± SD of three independent measurements (n = 3).

Figure 8

Cellular growth of T. marina AC16-MESO at different salt concentrations of 0.6, 1.25, 2.5, 5, 15, 30, 45, 60, 90, 120, and 35 (control) (‰). Squares (■) indicate significant negative differences in the growth respect to the control, with a confidence level of 95%, n = 3, p < 0.05.

Figure 9

Neutral lipid fluorescence of the strain T. marina AC16-MESO with Nile Red expressed in relative fluorescence units (RFU) and micrograph detail (100× magnification) of the microalgae stained. (A) Bright-field image and (B) UV micrograph of the microalgae stained with Nile Red at 35‰ salinity (control). Asterisks (*) indicate significant positive differences in the RFU with respect to the control; squares (■) indicate significant negative differences in the RFU with respect to the control, with a confidence level of 95%, n = 3, p < 0.05.