L29 Microbial Population Growth

Vocabulary flashcards covering key terms from the lecture on microbial population growth, including binary fission, growth phases, nutritional requirements, and methods of study.

Binary Fission (the prokaryotic “mitosis”)

Asexual reproduction by cell division in prokaryotes, resulting in two genetically identical cells.

Why prokaryotes are so dominant

Smaller genome= faster replication (13 minute doubling time) so evolve/adapt fast eg. antimicrobial resistence. Fast growth+ 3.5 billion years= colonization of all ecosystems.

Microbial growth

Not much different from eukaryotes in cellular requirements. Microbes need the same building blocks, just in different amounts, when supplied with all required materials they can reproduce via binary fission.

Closed Batch Culture System “classic” microbial growth

Standard method of studying microorganisms in culture with a defined, limited supply of nutrients. Once used, cells cannot proliferate. Bias towards fast growing organisms eg paothogens.

Lag Phase

Initial phase in a batch culture where cells require time to initiate biosynthetic reactions before active division. Length depends on history of inoculum.

Exponential (Log) Phase

Cells are actively dividing with no growth limitations. Population doubles in a constant time interval under ideal conditions.

Stationary Phase

Cells stop growing; cryptic growth is observed with an equilibrium between growing and dying cells (dynamic population).

Cryptic growth

Organisms survive by consuming lysed cell constituents of other dead cells within the culture.

Death Phase

Cell death occurs, and equilibrium is skewed towards death.

Carbon Source (material to build with)

Building blocks for macromolecular synthesis required for microbial growth.

Energy Source (to build)

Energy (electrons) to drive anabolic and catabolic reactions in the cell required for microbial growth.

Reducing Power

Carriers of energy/electrons (NAD+/NADP+) required for microbial growth. (NADH=reduced form)

source of carbon and energy

Light reaction, light energy transformed into NADPH and ATP. Harvest carbs from autotrophs as enery/carbon sources. Redox reactions.

Redox reactions

Chemical energy stored in bonds, when broken can be captured in new bonds (ATP), can be broken for later use. This (re)duction and (ox)idisation of coupled compounds can be applied to many compounds.

Trophic (nourishment) groups in microbiology

Carbon source; carbon dioxide= (auto), organic compound- (hetero). Energy source; light= (photo), Chemical compounds= (chemo). Add troph to the end.

Auxotroph

An organism that is unable to synthesize one or more essential growth factors, and it will not grow unless limiting factor is provided

Wild type strain

Has all essential genes, can grow by itself, can be isolated into pure culture.

Cross-feeding (Syntrophy)

When one species gains metabolic products of another species, allowing for survival of auxotrophs. Interactions can benifit one or both species. Common in nature and partially explains inability to culture most microbes.

Microbiome

The complete collection of microorganisms, and their genes, within a particular environment.

Microbiota

Individual microbial species in a biome – bacteria, fungi, archaea and viruses.

Culture-dependent methods (using pure cultures)

Relies on culturing of microbes in the lab. Pro: Can study one organism at a time, allows access to phenotype, can manipulate environment to see response. Con: Not all organisms can be cultured, too many species to grow them all, inconsistent with real world conditions, requires precise conditions to match microbiome needs.

Culture-independent methods (uses sequencing or metabolic profiling)

Relies predominantly on nucleic acid-based methods. No culturing required. Pro: Can study many organisms at a time, allows acces to genotype, shows communities as they are in nature, can target non-culturable organisms, provides access to unknown info/species. Con: No pure culture so no ability to manipulate, expensive and complex methods.