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[AgriLife Today] Bacteria battle: How one changes appearance, moves away to resist the other

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By: Kathleen Phillips

COLLEGE STATION — Two types of bacteria found in the soil have enabled scientists at Texas A&M AgriLife Research to get the dirt on how resistance to antibiotics develops along with a separate survival strategy.

The study, published in the journal PLoS Genetics this month, identifies an atypical antibiotic molecule and the way in which the resistance to that molecule arises, including the identity of the genes that are responsible, according to Dr. Paul Straight, AgriLife Research biochemist.

Straight and his doctoral student Reed Stubbendieck observed a species of bacteria changing its appearance and moving away from a drug to avoid being killed.

Straight’s lab on the Texas A&M University campus in College Station in general focuses on understanding how communities of bacteria interact with each other and other microbes.

“Over the past few decades, scientists have come to understand that bacteria aren’t just single individual cells that somehow cause infections or degrade toxins, for example,” Straight said. “In fact, they are populations and communities of many, many cells, whether just a si

Two types of bacteria found in the soil have enabled scientists at Texas A&M AgriLife Research to get the dirt on how resistance to antibiotics develops along with a separate survival strategy. (Texas A&M AgriLife photo by Kathleen Phillips)

Two types of bacteria found in the soil have enabled scientists at Texas A&M AgriLife Research to get the dirt on how resistance to antibiotics develops along with a separate survival strategy. (Texas A&M AgriLife photo by Kathleen Phillips)

ngle species of bacteria or a very diverse community. We are most recently aware of this in terms of the human microbiome. People have more bacteria cells in them than they have human cells.”

Reed Stubbendieck, Texas A&M University graduate student. (Texas A&M AgriLife photo by Kathleen Phillips)

Reed Stubbendieck, Texas A&M University graduate student. (Texas A&M AgriLife photo by Kathleen Phillips)

 

 

 

 

 

 

 

But what has not been fully understood about bacteria and microbes in general, he said, is the way in which they form these types of communities with more than one species.

“It’s both an ecological and a mechanistic bacteriology question,” Straight said. “For nearly 100 years, we’ve known that bacteria can produce molecules that can block the growth of other organisms including other bacteria, and those molecules have been very useful as antibiotics.”

Straight said the common understanding of the usefulness of antibiotics, however, sidestepped the ecological dynamics of the bacteria themselves in how they form communities, and interact with each other.

“We wanted to know what happens when we put two bacterial species together to compete with each other and use that model as a way to identify new molecules, identify pathways, or gene functions, that are required for the bacteria to survive under competitive stress,” he explained. “Identification of interesting new molecules or bacterial mechanisms of control that one might exploit can lead to developing a new antibiotic.”

For this study, Stubbendieck put together two species of non-pathogenic, soil-borne bacteria, Streptomyces and Bacillus subtilis, in different ways in the laboratory. He monitored the bacteria for different patterns in growth, motility and other factors when the organisms were together as opposed to when they were separate.

Stubbendieck noticed that the two bacteria would grow as expected in each colony initially, but over time one of the bacteria colonies would start to destroy the other one.

“It was very visual,” Straight said. “It would cause lysis, meaning that the cells inside the dying colony would be dissolved, leaving a mark of where this had happened.”

Stubbendieck had to identify the molecule or other functions that are responsible for causing the destruction, thus the way in which resistance might emerge.

“The molecule turned out to be very strange. It doesn’t look like any of the familiar antibiotics,” Straight said. “We find it interesting, because its chemical structure suggests it’s probably functioning in a way that is very different from the common antibiotics that are used.”

https://youtu.be/qee5CEAIgNA

Stubbendieck also noted that in the region where the cells were destroyed, there developed “little teeny colonies of bacteria” growing, indicating that they’re resistant to the molecule. So he picked a number of those colonies and sequenced the genomes, which found the mutations that cause resistance.

“I put a bunch of the cells with mutant bacterial stains on a petri dish together, and when I came in the next morning and looked in the incubator, I saw a difference between the mutants and the non-mutant strain that was night and day, and we knew we are on to something,” Stubbendieck recalled.

“With two pieces of the puzzle — the molecule itself identified plus a way in which the resistance to that molecule would arise, including the identity of the genes that are responsible for resistance — Reed was able to dissect the pathway of resistance,” Straight said. “And it turns out that in a B. subtilis membrane, proteins work as signaling systems for lots of different things. They can receive signals from the external environment, signals from other bacteria, signals telling them about the status of their cell in a fluctuating environment.

“If something damages a membrane, bacteria have a way of sensing that and then turning on the response,” Straight said.

All of the mutations Stubbendieck identified were in the same gene that encodes for a protein in the membrane that functions like a signaling protein, or it has a partner that it talks to, and all mutations turned on the signaling system. And, because the mutants had proteins that were turned on all the time, the drug that previously would have been effective could no longer kill the bacteria.

Additionally, not only did the researchers see that resistance could emerge that way but also the population of the B. subtilis, the one that’s typically killed by the drug, changed in appearance.

“It had morphological shapes and structures to it, which suggested that this organism had undergone a really profound change. That allowed it not only to be resistant to this drug, which causes lysis, but also to move as a population of bacteria across the agar surface in a petri dish,” Straight said.  

“This shows a way that organisms can interact with each other in a competitive, dynamic environment that’s  very different from the way we typically think about antibiotics,” he added. “It is not just a simple, one-way street of a molecule that’s produced and causes growth inhibition of the pathogen, and the pathogen can become resistant and that might be a problem for health reasons. What we’re seeing here are molecules that can function like an antibiotic and cause something like lysis, or cell death. And the organisms can use not just one resistance function but a combination of responses as a way of circumventing a competitive crisis.”

“This helps scientists build a much more mechanistically detailed picture of the competitive dynamics between bacteria, which helps us understand what happens in soil or inside a human intestine,” Straight added. “It helps us start to get a better image to work from when we talk about the role of microbes in the environment and the way competitive interactions structure microbial communities; how something becomes resistant and therefore how we might control that.”

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                                                                          American Lotus

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By Tony Dean

Farmers and ranchers are in a very close partnership with Mother Nature. If we really pay attention, she presents us some interesting scenarios.

For example, though they are totally different types of plants, water lilies and prickly pear have a lot in common. They both have strikingly beautiful flowers, both plants are edible, both of them are invaders into their respective habitats, and too much of either one can be an obstacle that we have to deal with.

Many north Texas ranches rely on excavated ponds for livestock water. Any time a pond contains a significant amount of shallow water so that sunlight reaches the bottom, some type of pond weed will develop.  The plant family that includes water lilies and lotuses is a common invader in our livestock water.

Water lilies and lotuses are in the same plant family but they are two separate genera. There are easy ways to tell them apart:

  • A primary difference is that water lily leaves commonly float on the surface, but lotus leaves can grow above the water line.
  • Water lily leaves and flowers are thick and waxy, while lotus leaves and flowers are thin and papery.
  • Water lily leaves have a distinct notch in the leaf, while lotus leaves are more rounded.
  • Water lily flower petals are pointed, and lotus petals are more rounded.

The photos attached to this writing are from Clay County, and this plant is common across north Texas. American lotus is adapted to a wide area, from Honduras north through Mexico and across the eastern US and into Canada.

American lotus is a perennial, and it is cold tolerant and heat tolerant. It can grow in any pond or slow moving stream that contains shallow water areas.  It prefers water with a depth of about 12 inches. Germination can occur from the large lotus seeds. Tubers, or roots, are established in the mud, and long slender stems extend upward. Leaves and flowers are both emergent in that they grow above the water line.

Lotus flowers are fragrant, and yellowish white with rich gold centers.  They open in the morning and close by late afternoon, then open again the next day.

Lotus is an edible plant and has a history as a food source. The large tuberous roots, the size of a human arm, were baked like sweet potatoes. The leaves were eaten like spinach, and the large seeds were ground into flour. Stems taste somewhat like beets and were usually peeled before being eaten.

There is a large world-wide industry of cultivating lilies and lotuses in water gardens. According to        Dr. Jerry Parsons, Professor and Extension Horticulturist with Texas A&M AgriLife Extension, cultivation of these plants dates back as early as ancient Egypt. Today, anyone with determination and a little money can have a water garden.

In 2011, the 82nd Texas Legislature designated the water lily “Texas Dawn” as the official Texas State Water Lily. Texas Dawn is a hybrid developed by Texas resident Kenneth Landon, a world-renowned expert in the field of water lilies and the director of the International Water Lily collection in San Angelo.

Ducks and other wildlife utilize the large acorn like seeds of American lotus, and submerged portions of all aquatic plants provide some form of wetland habitat. Many of us have tried to pull a bass out of a group of water lilies or lotuses, and I’m sure others have had better luck than I did. Although there can certainly be benefits to lilies, lotuses, and other aquatic plants, they can also infest ponds to the extent that the pond is not functioning correctly.

So, while the rest of the world works hard to grow these plants, ranchers sometimes need to control populations in their stock ponds. Once it gets a foot hold, American lotus can spread aggressively in wetland areas.

The primary issue that encourages American lotus, and most other water weeds, is shallow water.  Look closely at a good livestock pond and you will find that the deeper water is basically free of infestation.  Any pond will have a certain amount of shallow water that encourages water weed growth, depending upon the terrain at the pond site and how the pond was constructed. Some ranchers who enjoy and utilize wetland habitat may prefer to have ponds with significant shallow water area.

Almost all livestock ponds have a certain life expectancy.  Siltation, or movement of soil into the pond bottom through rainfall runoff, is a natural occurrence.  How fast siltation occurs into each pond, and how deep the pond was to start with, determines the length of time that the pond will contain adequate depth for dependable water for livestock.

Ponds that develop infestations of water weeds over a large percent of the surface may not have adequate depth to remain a viable water source for livestock during drought periods, especially in  western north Texas where evaporation rates are higher.

Mud, or silt, from the pond bottom, can be removed to deepen the water, but this is a very expensive process.  It is often more economical to construct a new pond rather than try to remove the silt from an old one.  Most of us do not have the funds to continually construct deep water livestock ponds, so we must try to keep existing structures functioning and providing good drinking water for livestock, for as long as we can. Control of pond weeds like American lotus may be necessary, and it can be accomplished.

There is currently no feasible biological control. American lotus can be cut and removed, but this process us usually temporary because lotus can reestablish from seeds and roots.

American lotus can be safely controlled by chemicals. This must be done carefully.  If a pond containing a large amount of any pond weeds is treated to remove all of the vegetation, a fish die-off could occur.  When the dying weeds decompose, they use up the oxygen in the water and fish can suffocate. If possible, treat only a portion of the area, wait about two weeks, and treat another portion.

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Tracks in the Sand

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This morning, I walked out into my arena and noticed something that gave me pause. The roping steers had been in there the day before, and even though the ground was wide and level, the sand carried their story. Hoofprints crossed every direction, but in several spots, the same trail was pressed deeper than the rest. Twelve steers had been turned out, yet more than a few chose the exact same path, wearing it down until it stood out from all the other tracks.

Cattle are creatures of habit. Anyone who has spent time around them knows this. They like routine: the same feed, the same water trough, the same shade tree in the pasture. When they are turned loose, they rarely wander without purpose. More often than not, they move together, following the same course as the steer in front of them. There are reasons for this: efficiency, safety, instinct. Walking a beaten path conserves energy, and following the herd is their natural defense. Even in an arena with no real destination, those instincts come through. By the end of a short turnout, you will see the evidence, lines where they have chosen the easiest way to travel and stuck with it.

Out on the range, those lines last longer. Before fences and highways, cattle drives cut deep paths across the land. The Chisholm Trail, which carried herds north from Texas through Oklahoma into Kansas, was walked by millions of cattle in the late 1800s. More than a century later, faint traces of those trails remain, worn so deep by hooves and wagon wheels that the land still carries the mark. On ranches today, you can see the same effect in pastures where cattle walk the same lines between water and grazing. From the ground those trails might look like nothing more than dusty ruts, but from the air, they sometimes stand out as sharp lines winding through otherwise open fields. Cattle do not simply pass over the land; they shape it. Every step adds up.

That simple truth extends beyond livestock. We all make tracks. Our habits and routines are our trails, worn in by repetition, sometimes efficient, sometimes limiting. Like the cow paths, they can serve a purpose, keeping us steady and helping us move forward. But when repeated without thought, they risk becoming ruts, keeping us from stepping into new ground. History offers perspective here too. The old cattle trails built towns and economies, but once railroads and fences changed the landscape, those paths were no longer useful. Sticking to them would have meant going in circles. Progress required something new.


The Tracks We Leave

Standing in the arena, I thought about the kind of tracks I leave behind. Most of mine are not visible in the dirt. They are pressed into my daily life, how I work, the way I handle challenges, the example I set. Some are helpful and worth keeping. Others may have outlived their purpose. The difference comes in knowing when to stay in the track and when to step out of it.

Tomorrow I will drag the arena and smooth it all clean again. The next time the steers are turned in, they will make the same trails. That is their nature. But unlike them, I have a choice. I can decide which paths are worth walking, which ones to change, and what kind of tracks I want to leave for others who might follow.

Tracks tell a story. Sometimes they are only temporary, fading with the next rain. Other times they last for generations, reminders of where herds and people once walked. This morning, the cattle showed me again that even the smallest things on the ranch carry meaning. Their tracks in the arena were not just marks in the sand. They were a lesson: every step matters, and the paths we choose shape more than just the ground beneath our feet.

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Leopold’s Legacy: The Five Tools That Shaped Conservation

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By Raenne Santos

Known as the father of wildlife management, Aldo Leopold’s teachings reshaped our understanding of conservation and our role in nature. His philosophy, rooted in ethics, ecology, and action, emerged in response to the environmental degradation of the early 20th century in the American West. Overgrazed pastures, eroding soils, and changing wildlife populations revealed the consequences of treating natural resources as limitless. 

Recognizing these challenges, Leopold theorized a transformative approach to land stewardship, emphasizing that the land is not merely a commodity, but a community in which we all belong. His works, A Sand County Almanac and Land Ethic, are still referenced to this day by modern conservationists. In Land Ethic, he introduced a practical framework for wildlife management known as the Five Tools of Wildlife Management, which offers land stewards a structured approach to maintaining and restoring ecological balance.

Symbolizing brush management, the axe is one of Leopold’s tools for controlling invasive species, shaping habitats, and mitigating wildfire risks. By selectively removing vegetation, land managers can enhance biodiversity, create open spaces for native species, and maintain healthy ecosystems. 

Representing grazing animals, the cow (when used properly) mimics the natural disturbances once provided by bison. Grazing animals promote healthy ecosystems by aiding in nutrient cycling and soil disturbance. Responsible grazing practices prevent overuse and contribute to sustainable land management. 

The plow signifies mechanical disturbance and soil preparation, crucial for habitat restoration and agricultural productivity. Used strategically, it aids in cultivating crops and creating conditions favorable to wildlife. However, misuse can lead to erosion, requiring careful application in conservation efforts.

Fire, a powerful natural tool, plays a crucial role in maintaining biodiversity and landscape resilience. Land managers use prescribed fire to control invasive species, rejuvenate plant communities, and shape habitats. Fire promotes the natural cycles of ecosystems and supports species diversity. 

The final tool, the gun, is used to manage game populations and control predators. During Leopold’s time, unregulated hunting contributed to species extinction and posed threats to others. Today, hunting is strictly managed through game laws and seasonal regulations to ensure sustainable populations.

Leopold’s Five Tools of Wildlife Management continue to influence conservation practices today. While techniques have evolved, the fundamental principles remain the same—balancing human involvement with ecological processes to sustain healthy ecosystems. His approach emphasizes the importance of working with nature rather than against it. By embracing ethical land stewardship, modern conservationists honor Leopold’s vision, ensuring that future generations inherit thriving landscapes.

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