Lecture Notes: Microbes in the Environment and Photosynthesis

Administrative Announcements

• Attendance
  • Two attendance grades: Top Hat (informational) and Active Learning Points (counts towards grade).
  • Contact instructor if attendance recording issues arise.
• Exam 3
  • Online, available April 9th to 12th.
  • Covers regulation and microbes in the environment.

Microbes in the Ocean

• Ocean Sampling
  • Terra Oceans Foundation has globally sampled oceans.
  • Different ocean environments vary due to weather and land masses.
• Phylotypes and Reads
  • Dominant genera pattern: few dominant, many minor.
  • Dominant genera in oceans: Polygobacter, Prochlorococcus, Synchrococcus, Burkholderia, Shiwanella.

Focus on Specific Genera

• Polygobacter
  • Ubiquitous, oligotroph, grows slowly in low nutrient seawater medium.
  • Contains proteorhodopsin for generating energy.
• Cyanobacteria (Prochlorococcus and Synchrococcus)
  • Photosynthetic, grow on light.
  • Prochlorococcus: 0.6 micron, inhabits subtropical/tropical oceans.
  • Synchrococcus: larger, found in all oceans, diverse, obligate photoautotrophs.

Photosynthesis Overview

• Light Harvesting Complexes
  • Composed of protein and pigments (chlorophyll, bacterioclorophyll).
  • Collect light and focus on reaction center.
• Reaction Center
  • Converts light energy to high-energy electrons.
  • Electron transport chain pumps protons and generates ATP.

Pigments & Carotenoids

• Chlorophyll
  • Different absorption spectra for chlorophyll and bacterioclorophyll.
• Carotenoids
  • Protect structures from reactive oxygen species.

Types of Photosynthesis

• Anoxygenic
  • No oxygen production, various electron sources (e.g., H2S).
  • Includes purple bacteria, green bacteria, heliobacteria.
• Oxygenic
  • Produces oxygen, uses water as electron source.
  • Includes cyanobacteria.

Bacteria Examples

• Purple Bacteria
  • Found in freshwater/marine environments.
  • Versatile growth: photoautotrophically, heterotrophically, etc.
  • Photosystem housed in intercytoplasmic membrane.
• Green Bacteria
  • Obligate phototrophs, use chlorosome for efficient light collection.
  • Example: Chlorobaceae.
• Cyanobacteria
  • Ubiquitous, obligate phototrophs, oxygenic photosynthesis.
  • Found in diverse environments including hot springs.

Photosynthesis Summary

• Essential Parts: Light harvesting complex, electron source, reaction center, electron transport chain, ATP production, NADPH synthesis.
• Comparisons
  • Retinal-based phototrophy vs. photosynthesis similarities and differences.

Conclusion

• Encourage review and understanding of photosynthesis processes and key microbial genera.