Microbial Community Lecture, Lecture notes of Biology

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Influences on Microbial

Activity in Stream

Ecosystems

BIO 571

Aaron Mrotek, Danny Kimball, Courtney Roush,

Zasha Welsh

Review ● (^) Microbes= Bacteria + Fungi ● (^) Decomposers ● (^) Respire CO ● (^) Obtain nutrients from leaves and water column. ● (^) Microbes assimilate more nutrients from fast-decomposing leaves. ● (^) Nutritious for macroinvertebrates eating leaf litter colonized by microbes

Wymore et al. (2016) METHODS: ● (^) Replicated genotypes of P. fremontii and P. angustifolia ● (^) Concentrations of tannins, lignins, lignin/N ratios determined ● (^) Litter bags; removed at 6, 14 and 28 days ● (^) 16S rRNA analysis used to determine species abundance ● (^) Non metric multidimensional scaling

Wymore et al. (2016) RESULTS:

1. Significant difference between bacterial composition based on litter species characteristics but not genotype. 2. No significant difference between genotypes amongst same species. 3. Yes. Time in stream played large part in variation. 4. Bacterial diversity increase over time but liable litter showed greater diversity.

What we found in our articles - Wymore et al. (2013) ● (^) rRNA gene abundance ● (^) Bacteria= 16S rRNA gene abundance ● (^) Fungi= 18S rRNA gene abundance ● (^) HYPOTHESES: Litter Type rRNA gene abundance Defensive Cmpds Overall abundance P. fremontii 16S^ ↓ Bacteria P. angustifolia 18S^ ↑ Fungi

Wymore et al. (2013) Cont’d RESULTS: ● (^) Fig. ○ (^) Supports hypothesis ○ (^) Bacterial 16S rRNA 4x more abundant on P. fremontii ○ Fungal 18S rRNA 8x more abundant on P. angustifolia

Rowe et al. Background

• How does acidic mine water

affect microbial communities?

• Abandoned mines acidified

streams (pH~2.6)

• Assessed microbial

communities at different

stream depths

• Iron and Sulfur

Rowe et al. Findings

• Sulfur mine- microbes convert sulfur to sulfuric acid,

increasing acidity.

• Primary producers are iron and sulfur oxidizing

prokaryotes

• Different communities will inhabit the four strata of

the stream.

• Top layer will consist of acidophilic algae (CL1)
• CL4 color and community composition very different

Figure 2 Biodiversity ↑ distance from mine→ ↑ Sunlight→ ↑Photosynthesis→ ↑O 2 & DOC→ ↑Energy Source→ ↑HB→ Grey- Acidophilic heterotrophic bacteria Black- Iron- oxidizing bacteria

Figure 6 Geochemistry CL2 was able to reduce the most iron in the presence of 0 2 CL3 & 4 are able to reduce the most Fe without O 2

Summary

• Increase in biodiversity the further you get from the adit, but

not as much as in non acidic streams (specialization).

• Specialized microorganisms- primary producers’ energy source

is ferrous iron and reduced sulfur

• Biodiversity increases as streamers increase because they

increases the amount DOC and O 2.

• Main source of energy changes the primary producers of a

stream.

• Iron and sulfur the main energy source yield unusual

nutrient cycling

Cheever et al. (2013) ● (^) N assimilated from leaf vs N immobilized from water column by microbes ● (^) 5 Appalachian streams ranging in N concentrations Takeaways: ○ (^) Rapid decomposition with increased N availability ○ (^) Microbes initially acquire N from leaf litter ○ (^) Later in decomposition, microbes rely more on N in streamwater for microbial growth ○ (^) Predominant source of N for microbes is streamwater, even in streams with low N conc.

Pastor et al. (2014) - Hypothesis

Pastor et al. (2014) - Hypothesis ● (^) Microbes growing on litter with a higher content of recalcitrant compounds would show a relatively greater reliance on C and N from streamwater than those growing on leaves with a lower content of recalcitrant compounds ○ (^) Because recalcitrant compounds are a less-accessible resource for heterotrophic microbes