Document Type



Doctor of Philosophy (PhD)



First Advisor's Name

Evelyn Gaiser

First Advisor's Committee Title

co-committee chair

Second Advisor's Name

Miroslav Gantar

Second Advisor's Committee Title

co-committee chair

Third Advisor's Name

Haywood Dail Laughinghouse IV

Third Advisor's Committee Title

committee member

Fourth Advisor's Name

Kathleen Rein

Fourth Advisor's Committee Title

committee member

Fifth Advisor's Name

Mauricio Rodriguez-Lanetty

Fifth Advisor's Committee Title

committee member


lipids, fatty acids, mitochondria, bacteria, Lake Okeechobee, alkaliphilic

Date of Defense



Diatoms are excellent biological models of growth and intracellular oil generation. The productivity and compounds of diatoms, especially oils, support aquatic food chains and human medical and industrial needs. The qualities that made diatoms prolific producers, specifically diatom physiological features such as growth rates with intracellular lipid storage in alkaline environments, are however poorly understood. Another physiological aspect that remains unexplored is the effects of bacteria on the growth and lipid production of alkaliphilic diatoms. More studies, especially co-cultures, are needed for advances in diatom biology and strain performance for the algal biotechnological field. Besides physiology, diatom genetics using next-generation methods are used to reveal the basis for diatom success in growth and productivity, though more genomic data and comparative studies are needed to fully uncover these mechanisms in diatoms. To improve our understanding of alkaliphilic diatom physiology and genetics, specifically we need to understand 1) what stimulates diatom successful growth in alkaline environments and in culture, 2) diatom biodiversity especially at the species level, 3) algal physiology in the context of how diatom productivity may be enhanced by bacteria, and 4) the biological basis for the extraordinary growth rates of diatoms and their success in alkaline environments.

To explore ways in which we can improve our understanding of alkaliphilic diatom physiology and genetics this dissertation aimed to first isolate alkaliphilic algae and explore their alkalinity optimums along with their growth rates and lipid production. A high lipid producing diatom Fistulifera alcalina was isolated and characterized using 18S rRNA and rbcL molecular phylogeny. To further explore the diversity within Fistulifera and simultaneously exploit diatom microbiomes, Lake Okeechobee was sourced for alkali-tolerant to alkaliphilic bacteria associated with diatoms to co-culture with F. alcalina. Results indicated that alkaliphilic bacteria like Bacillus horikosshi were effective in modulating growth and lipid content of F. alcalina. To explore the basis for the extraordinary growth rates in F. alcalina and its’ success in alkaline environments, the mitochondrial genome was sequenced and compared to F. solaris. Results indicate that alkaliphilic diatoms may have streamlined genomes and are impetus for further genome sequencing and physiological studies.



Previously Published In

Berthold D.E., De La Rosa N., Engene N., Gantar M., Shetty K., Jayachandran J., Laughinghouse IV H.D., (2020) Omega-7-Producing Alkaliphilic Diatom Fistulifera sp. 154-3 from Lake Okeechobee, FL. Algae, 35(1): 91-106.

Berthold, DE; Frankovich, T; Gaiser, E; Laughinghouse IV, HD. (2020) Fistulifera alcalina sp. nov. (Naviculales, Stauroneidaceae) a new alkaliphilic diatom species from Lake Okeechobee, Florida (USA). Diatom Research 35(3): 301-311. doi: 10.1080/0269249X.2020.1801517.

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