Microbiology Chapter 15: Bacterial Diversity

Questions and Answers

What is the primary purpose of 16S ribosomal RNA (rRNA) gene sequences in bacterial research?

To determine the ecological diversity of environments

To classify bacteria by their metabolic rates

To characterize all known bacterial species in laboratory cultures

To identify bacterial phyla based on their genetic material (correct)

Which of the following statements about cultivated bacterial species is correct?

More than 90% of cultivated species belong to four dominant phyla. (correct)

Cultivated species are predominantly found in environments lacking diversity.

All major bacterial phyla are equally represented in laboratory cultures.

Less than 90% of cultivated species belong to five major phyla.

Which of the following four phyla represents the overwhelming majority of cultivated bacteria?

Spirochaetes

Firmicutes (correct)

Cyanobacteria

Chlamydiae

How many bacterial phyla are the focus of exploration in this chapter?

20 Signup and view all the answers

What does the vast number of described bacterial species indicate about the scope of bacterial diversity?

There is significant diversity within bacteria that cannot be fully represented. Signup and view all the answers

What is a key characteristic of the bacterial phyla selected for exploration in this chapter?

Phyla with the largest numbers of characterized species Signup and view all the answers

What role do phylogenetic trees play in the study of bacterial diversity?

They guide the discussion of bacterial diversity among various species. Signup and view all the answers

Which of the following best describes the ecological diversity mentioned in relation to bacterial species?

The different physical environments where bacteria exist Signup and view all the answers

What distinguishes Proteobacteria from other bacterial phyla?

They are the largest and most metabolically diverse phylum. Signup and view all the answers

Which statement accurately describes the significance of Proteobacteria in various fields?

They play a major role in medicine, industry, and agriculture. Signup and view all the answers

Which energy-generating mechanism is utilized by chemolithotrophic species of Proteobacteria?

Oxidizing inorganic compounds. Signup and view all the answers

What is the predominant structural feature of all Proteobacteria?

They are gram-negative bacteria. Signup and view all the answers

Which type of species among Proteobacteria does NOT participate in methanogenesis?

Methanogenic Archaea Signup and view all the answers

What sets Proteobacteria apart in the context of characterized species?

They account for more than a third of all characterized bacterial species. Signup and view all the answers

Which bacterial metabolic process is notably absent in Proteobacteria?

Oxygenic phototrophy Signup and view all the answers

In terms of phylogenetic diversity, how many classes are Proteobacteria divided into?

Six classes Signup and view all the answers

Which metabolic process is specifically associated with Nitrospirae?

Complete ammonia oxidation (comammox) Signup and view all the answers

Which class of Proteobacteria includes only a single characterized species?

Zetaproteobacteria Signup and view all the answers

Which of the following terms represents the highest level of hierarchy in microbial systematics?

Domain Signup and view all the answers

What type of organism thrives in environments with low oxygen levels?

Microaerophilic species Signup and view all the answers

Which of the following cell shapes is NOT typically associated with Proteobacteria?

Square Signup and view all the answers

Which metabolic process is characterized by the oxidation of ammonium without the use of oxygen?

Anammox Signup and view all the answers

Which class of Proteobacteria is associated with notable morphological diversity in bacterial life forms?

Gammaproteobacteria Signup and view all the answers

What specific feature differentiates facultatively aerobic species from strict anaerobic species?

Capacity to grow with or without oxygen Signup and view all the answers

Study Notes

Distinctions in Diversity

Metabolic, ecological, and phylogenetic diversity are distinct concepts in biology.
Current focus is on major lineages of Bacteria.
Chapter 17 will delve into Archaea and Chapter 18 will focus on microbial Eukarya.

16S rRNA Gene Sequences

16S rRNA gene sequences are crucial for identifying bacterial phyla from environmental samples.
Over 80 bacterial phyla identified; only about 30 phyla have species characterized in labs.
Figure 16.1b illustrates the concentration of cultivated genera.

Cultivated Bacterial Species

Over 90% of cultivated bacterial species belong to four main phyla: Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes.
Figure 16.1b shows dominance of these phyla, emphasizing their significance.

Diversity of Bacterial Species

More than 12,000 species of bacteria have been described, making exhaustive coverage impractical.
Phylogenetic trees aid in understanding bacterial diversity across various phyla.

Selected Bacterial Phyla for Exploration

Focus on 20 bacterial phyla with a significant number of characterized species and diversity.

Proteobacteria: Overview

Proteobacteria is the largest and most metabolically diverse phylum of Bacteria.
It includes six classes: Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Epsilonproteobacteria, and Zetaproteobacteria.

Significance of Proteobacteria

Accounts for over a third of all characterized bacterial species.
Significant roles in medicine, industry, and agriculture.

Gram-Negative Characteristics

All Proteobacteria are classified as gram-negative bacteria.

Metabolic Diversity

Proteobacteria display various energy-generating mechanisms:
- Chemolithotrophic: Energy from oxidizing inorganic compounds.
- Chemoorganotrophic: Energy from oxidizing organic compounds.
- Phototrophic: Energy derived from light.
Notable metabolic processes absent in Proteobacteria include:
- Methanogenesis: Exclusive to Archaea.
- Oxygenic phototrophy: Found in Cyanobacteria.

Oxygen Relationships

Wide variation in oxygen relationships:
- Anaerobic species do not require oxygen.
- Microaerophilic species thrive in low oxygen.
- Facultatively aerobic species can grow in both conditions.

Morphological Diversity

Proteobacteria exhibit extensive morphological diversity:
- Cell shapes include straight rods, curved rods, cocci, spirilla, filamentous, budding, and appendaged forms.

Microbial Systematics

Understanding hierarchy in microbial systematics is essential:
- Levels: Domain, Phylum, Class, Order, Family, Genus, Species.

Classification of Proteobacteria

Divided into six classes based on 16S rRNA sequences:
- Alphaproteobacteria
- Betaproteobacteria
- Gammaproteobacteria
- Deltaproteobacteria
- Epsilonproteobacteria
- Zetaproteobacteria includes only Mariprofundus ferrooxydans, a marine iron-oxidizing bacterium.

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Description

Explore the distinctions between metabolic, ecological, and phylogenetic diversity in bacteria in this quiz based on Chapter 15. Discover the major lineages of Bacteria and their significance, plus the upcoming focus on Archaea and microbial Eukarya in subsequent chapters.