Signals of aging associated with lower growth rates in Kluyveromyces lactis cultures under nitrogen limitation

Author:

Corrêa Lygia Fátima da Mata1,Passos Frederico José Vieira2,Viloria Marlene Isabel Vargas3,Filho Olindo Assis Martins4,de Carvalho Andréa Teixeira4,Passos Flávia Maria Lopes1

Affiliation:

1. Departamento de Microbiologia, Universidade Federal de Viçosa, Av. P.H. Rolfs s/n 36571-000, Laboratório de Fisiologia de Microrganismos, BIOAGRO, Viçosa – MG, Brasil.

2. Departamento de Tecnologia de Alimentos, Universidade Federal de Viçosa, Viçosa – MG, Brasil.

3. Departamento de Medicina Veterinária, Universidade Federal de Viçosa, Viçosa – MG, Brasil.

4. Laboratório de Biomarcadores de Diagnóstico e Monitoração, Fundação Oswaldo Cruz, Centro de Pesquisas René Rachou, Belo Horizonte – MG, Brasil.

Abstract

The effects of aging on the specific growth rate of Kluyveromyces lactis cultures, as a function of (NH4)2SO4 concentration, were evaluated. The growth kinetic parameters maximum specific growth rate and saturation constant for (NH4)2SO4 were calculated to be 0.44 h−1 and 0.15 mmol·L−1, respectively. Batch cultures were allowed to age for 16 days without influence of cell density or starvation. The specific growth rates of these cultures were determined each day and decreased as the population aged at different nitrogen concentrations. Aging signals (N-acetylglucosamine content of the cell wall, cell dimensions, and apoptosis markers) were measured. Apoptosis markers were detected after 5 days at limiting (NH4)2SO4 concentrations (0.57, 3.80, and 7.60 mmol·L−1) but only after 8 days at a nonlimiting (NH4)2SO4 concentration (38.0 mmol·L−1). Similarly, continuous cultures of K. lactis performed under nitrogen limitation and, at lower dilution rates, accumulated cells exhibiting aging signals. The results demonstrate that aging affects growth rate and raise the question of whether nitrogen limitation accelerates aging. Because aging is correlated with growth rate, and each dilution rate of the continuous cultures tends to select and accumulate cells with a respective age, cultures growing at lower growth rates can be useful to investigate yeast physiological responses, including aging.

Publisher

Canadian Science Publishing

Subject

Genetics,Molecular Biology,Applied Microbiology and Biotechnology,General Medicine,Immunology,Microbiology

Reference44 articles.

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4. Isolation and characterization of the gene encoding xylose reductase from Kluyveromyces lactis

5. Quantitative Physiology of Saccharomyces cerevisiae at Near-Zero Specific Growth Rates

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